Heroes of Science: Physicists

Cavendish devoted considerable attention to the subject of heat, especially thermometry. In many of his investigations on latent and specific heat he worked on the same lines as Black, and at about the same time; but it is difficult to determine the exact date of some of Cavendish's work, as he frequently did not publish it for a long time after its completion, and most of Black's results were made public only to his lecture audience. Cavendish, however, improved upon Black in his mode of stating some of his results. The heat, for instance, which is absorbed by a body in passing from the solid to the liquid, or from the liquid to the gaseous, condition, Black called "latent heat," and supposed it to become latent within the substance, ready to reveal itself when the body returned to its original condition. This heat Cavendish spoke of as being destroyed or generated, and this is in accordance with what we now know respecting the nature of heat, for when a body passes from the solid to the liquid, or from the liquid or solid to the gaseous, condition, a certain amount of work has to be done, and a corresponding amount of heat is used up in the doing of it. When the body returns to its original condition, the heat is restored, as when a heavy body falls to the ground, or a bent spring returns to its original form. Cavendish's determination of the so-called latent heat of steam was very slightly in error.

About 1760 very extraordinary beliefs were current respecting the excessive degree of cold and the rapid variations of temperature which take place in the Arctic regions. Braun, of St. Petersburg, had observed that mercury, in solidifying in the tube of a thermometer, descended through more than four hundred degrees, and it was assumed that the melting point of mercury was about 400° below Fahrenheit's zero. It then became necessary to suppose that, while the mercury in a thermometer was freezing, there was a variation of temperature to this extent, and thus these wild reports became current. Cavendish and Black independently explained the anomaly, and each suggested the same method of determining the freezing point of mercury. Cavendish, however, had a piece of apparatus prepared which he sent to Governor Hutchins, at Albany Fort, Hudson's Bay. It consisted of an outer vessel, in which the mercury was allowed to freeze, but not throughout the whole of its mass, and the bulb of the thermometer was kept immersed in the liquid metal in the interior. In this way the mercury in the thermometer was cooled down to the melting point without commencing to solidify, and the temperature was found to be between 39° and 40° below Fahrenheit's zero.

As a chemist, Cavendish is renowned for his eudiometric analysis, whereby he determined the percentage of oxygen in air with an amount of accuracy that would be creditable to a chemist of to-day, and for his discovery of the composition of water; but to the world generally he is perhaps best known by the famous "Cavendish experiment" for determining the mass, and hence the mean density, of the earth. The apparatus was originally suggested by the Rev. John Michell, but was first employed by Cavendish, who thereby determined the mean density of the earth to be 5·45. At the request of the Astronomical Society, the investigation was afterwards taken up by Mr. Francis Baily, who, after much labour, discovered that the principal sources of error were due to radiation of heat, and consequent variation of temperature of parts of the apparatus during the experiment. To minimize the radiation and absorption, he gilded the principal portions of the apparatus and the interior of the case in which it was contained, and his results then became consistent. Cavendish had himself suggested the cause of the discrepancy, but the gilding was proposed by Principal Forbes. As a mean of many hundreds of experiments, Mr. Baily deduced for the mean density of the earth 5·6604. Cavendish's apparatus was a delicate torsion-balance, whereby two leaden balls were supported upon the extremities of a wooden rod, which was suspended by a thin wire. These balls were about two inches in diameter, and the experiment consisted in determining the deflection of the wooden arm by the attraction of two large solid spheres of lead brought very near the balls, and so situated that the attraction of each tended to twist the rod horizontally in the same direction. The force required to produce the observed deflection was calculated from the time of swing of the rod and balls when left to themselves. The force exerted upon either ball by a known spherical mass of metal, with its centre at a known distance, being thus determined, it was easy to calculate what mass, having its centre at the centre of the earth, would be required to attract one of the balls with the force with which the earth was known to attract it.

Dr. Wilson sums up Cavendish's view of life in these words: —

His theory of the universe seems to have been that it consisted solely of a multitude of objects which could be weighed, numbered, and measured; and the vocation to which he considered himself called was to weigh, number, and measure as many of these objects as his allotted three score years and ten would permit. This conviction biased all his doings – alike his great scientific enterprises and the petty details of his daily life. Πάντα μέτρῳ, καὶ ἀριθμῷ, καὶ σταθμῷ was his motto; and in the microcosm of his own nature he tried to reflect and repeat the subjection to inflexible rule and the necessitated harmony which are the appointed conditions of the macrocosm of God's universe.

COUNT RUMFORD

Benjamin Thompson, like Franklin, was a native of Massachusetts, his ancestors for several generations having been yeomen in that province, and descendants of the first colonists of the Bay. In the diploma of arms granted him when he was knighted by George III., he is described as "son of Benjamin Thompson, late of the province of Massachusetts Bay, in New England, gent." He was born in the house of his grandfather, Ebenezer Thompson, at Woburn, Massachusetts, on March 26, 1753. His father died at the age of twenty-six, on November 7, 1754, leaving the infant Benjamin and his mother to the care of the grandparents. The widow married Josiah Pierce, junior, in March, 1756, and with her child, now a boy of three, went to live in a house but a short distance from her former residence.

Young Thompson appears to have received a sound elementary education at the village school. From some remarks made by him in after years to his friend, M. Pictet, it has been inferred that he did not receive very kind treatment at the hands of his stepfather. It is clear, however, that the most affectionate relationships always obtained between him and his mother, and the latter appears to have had no cause to complain of the treatment she received from her second husband, with whom she lived to a very good old age. That Thompson in early boyhood developed some tendencies which did not meet with ready sympathy from those around him is, however, equally clear. His guardians destined him for a farmer, like his ancestors, and his experiments in mechanics, which took up much of his playtime and in all probability not a few hours which should have been devoted to less interesting work, were not regarded as tending towards the end in view. Hence he was probably looked upon as "indolent, flighty, and unpromising." Later on he was sent to school in Byfield, and in 1764, at the age of eleven, "was put under the tuition of Mr. Hill, an able teacher in Medford, a town adjoining Woburn." At length, his friends having given up all hope of ever making a farmer of the boy, he was apprenticed, on October 14, 1766, to Mr. John Appleton, of Salem, an importer of British goods and dealer in miscellaneous articles. He lived with his master, and seems to have done his work in a manner satisfactory on the whole, but there is evidence that he would, during business hours, occupy his spare moments with mechanical contrivances, which he used to hide under the counter, and even ventured occasionally to practise on his fiddle in the store. He stayed with Mr. Appleton till the autumn of 1769, and during this time he attended the ministry of the Rev. Thomas Barnard. This gentleman seems to have taken great interest in the boy, and to have taught him mathematics, so that at the age of fifteen he was able "to calculate an eclipse," and was delighted when the eclipse commenced within six seconds of his calculated time. Thompson, while an apprentice, showed a great faculty for drawing and designing, and used to carve devices for his friends on the handles of their knives or other implements. It was at this time he constructed an elaborate contrivance to produce perpetual motion, and on one evening it is said that he walked from Salem to Woburn, to show it to Loammi Baldwin, who was nine years older than himself, but his most intimate friend. Like many other devices designed for the same purpose, it had only one fault – it wouldn't go.

It was in 1769, while preparing fireworks for the illumination on the abolition of the Stamp Act, that Thompson was injured by a severe explosion as he was grinding his materials in a mortar. His note-book contained many directions for the manufacture of fireworks.

During Thompson's apprenticeship those questions were agitating the public mind which finally had their outcome in the War of Independence. Mr. Appleton was one of those who signed the agreement refusing to import British goods, and this so affected the trade of the store that he had no further need for the apprentice. Hence it was that, in the autumn of 1769, Thompson went to Boston as apprentice-clerk in a dry goods store, but had to leave after a few months, through the depression in trade consequent on the non-importation agreement.

His note-book, containing the entries made at this time, comprised several comic sketches very well drawn, and a quantity of business memoranda which show that he was very systematic in keeping his accounts. His chief method of earning money, or rather of making up the "Cr." side of his accounts, was by cutting and cording wood. A series of entries made in July and August, 1771, show the expense he incurred in constructing an electrical machine. It is not easy to determine, from the list of items purchased, the character of the machine he constructed; but it is interesting to note that the price in America at that time of nitric acid was 2s. 6d. per ounce; of lacquer, 40s. per pint; of shellac, 5s. per ounce; brass wire, 40s. per pound; and iron wire, 1s. 3d. per yard. The nature of the problems which occupied his thoughts during the last year or two of his business life are apparent in the following letters: —

Woburn, August 16, 1769.

Mr. Loammi Baldwin,

Sir,

Please to inform me in what manner fire operates upon clay to change the colour from the natural colour to red, and from red to black, etc.; and how it operates upon silver to change it to blue.

I am your most humble and obedient servant,

Benjamin Thompson

God save the king.

Woburn, August, 1769.

Mr. Loammi Baldwin,

Sir,

Please to give the nature, essence, beginning of existence, and rise of the wind in general, with the whole theory thereof, so as to be able to answer all questions relative thereto.

Yours,Benjamin Thompson.

This was an extensive request, and the reply was probably not altogether satisfactory to the inquirer. On the back of the above letter was written: —

Woburn, August 15, 1769.

Sir

There was but few beings (for inhabitants of this world) created before the airy element was; so it has not been transmitted down to us how the Great Creator formed the matter thereof. So I shall leave it till I am asked only the Natural Cause, and why it blows so many ways in so short a time as it does.

Thompson appears now to have given up business and commenced the study of medicine under Dr. Hay, to whom for a year and a half he paid forty shillings per week for his board. During this time he paid part of his expenses by keeping school for a few weeks consecutively at Wilmington and Bradford, and another part was paid by cords of wood. His business capacity, as well as his dislike of ordinary work, is shown by some arrangements which he made for getting wood cut and corded at prices considerably below those at which he was himself paid for it. His note-book made at this time contains, besides business entries, several receipts for medicines and descriptions of surgical operations, in some cases illustrated by sketches. In his work he was methodical and industrious, and the life of a medical student suited his genius far better than that of a clerk in a dry goods store. When teaching at Wilmington he seems to have attracted attention by the gymnastic performances with which he exercised both himself and his pupils. While a student with Dr. Hay, he attended some of the scientific lectures at Harvard College. The pleasure and profit which he derived from these lectures are sufficiently indicated by the fact that forty years afterwards he made the college his residuary legatee.

Thompson won such a reputation as a teacher during the few weeks that he taught in village schools in the course of his student life, that he received an invitation from Colonel Timothy Walker to come to Concord, in New Hampshire, on the Merrimack, and accept a permanent situation in a higher grade school. It was from this place that he afterwards took his title, for the early name of Concord was Rumford, and the name was changed to Concord "to mark the restoration of harmony after a long period of agitation as to its provincial jurisdiction and its relation with its neighbours."

The young schoolmaster of Concord was soon on very intimate terms with the minister of the town, the Rev. Timothy Walker,5 a man who was so much respected that he had thrice been sent to Britain on diplomatic business. Mr. Walker's daughter had been married to Colonel Rolfe, a man of wealth and position, and, with the exception of the Governor of Portsmouth, said to have been the first man in New Hampshire to drive a curricle and pair of horses. Thompson soon married – or, as he told Pictet, was married to – the young widow. Whatever may have been implied by this other way of putting the question, there is no doubt that Thompson always had the greatest possible respect for his father-in-law, and ever remembered him with sincere gratitude. The fortunes of the gallant young schoolmaster now appeared to be made; when the engagement was settled, the carriage and pair were brought out again, and the youth was attired in his favourite scarlet as a man of wealth and position. In this garb he drove to Woburn, and introduced his future wife to his mother, whose surprise can be better imagined than described.

The exact date of Thompson's marriage is not known. His daughter Sarah, afterwards Countess of Rumford, was born in the Rolfe mansion on October 18, 1774. It is needless to say that the engagement to Mrs. Rolfe terminated the teaching at the school.

Thompson now had a large estate and ample means to improve it. He gave much attention to gardening, and sent to England for garden seeds. In some way he attracted the attention of Governor Wentworth, the Governor of Portsmouth, who invited him to the Government House, and was so taken with the former apprentice, medical student, and schoolmaster, that he gave him at once a commission as major. This appointment was the cause of the misfortunes which almost immediately began to overtake him. He incurred the jealousy of his fellow-officers, over whom he had been appointed, and he failed to secure the confidence of the civilians of Concord.

Public feeling in New England was very much excited against the mother country. Representations were sent to the British Government, but appeared to be treated with contempt. Very many of these documents were found, after the war was over, unopened in drawers at the Colonial Office. British ministers appeared to know little about the needs of their American dependencies, and relations rapidly became more and more strained. The patriots appointed committees to watch over the patriotism of their fellow-townsmen, and thus the freedom of a free country was inaugurated by an institution bordering in character very closely upon the Inquisition; and the Committees of Correspondence and Safety accepted evidence from every spy or eavesdropper who came before them with reports of suspected persons. Thompson was accused of "Toryism;" the only definite charge against him being that he had secured remission of punishment for some deserters from Boston who had for some time worked upon his estate. He was summoned before the Committee of Safety, but refused to make any confession of acts injurious to his country, on the ground that he had nothing to confess. His whole after-life shows that his sympathies were very much on the side of monarchy and centralization, but at this time there appears to have been no evidence that could be brought against him. The populace, however, stormed his house, and he owed his safety to the fact that he had received notice of their intentions, and had made his escape a few hours before. This was in November, 1774. Thompson then took refuge at Woburn, with his mother, but the popular ill feeling troubled him here, so that his life was one of great anxiety.

While at Woburn, his wife and child joined him, and stayed there for some months. At length he was arrested and confined in the town upon suspicion of being inimical to the interests of his country. When he was brought before the Committee of Inquiry, there was no evidence brought against him. Major Thompson then petitioned to be heard before the Committee of the Provincial Congress at Washington. This petition he entrusted to his friend Colonel Baldwin to present. The petition was referred by the committee to Congress, by whom it was deferred for the sake of more pressing business. At length he secured a hearing in his native town, but the result was indecisive, and he did not obtain the public acquittal that he desired, though the Committee of Correspondence found that the "said Thompson" had not "in any one instance shown a disposition unfriendly to American liberty; but that his general behaviour has evinced the direct contrary; and as he has now given us the strongest assurances of his good intentions, we recommend him to the friendship, confidence, and protection of all good people in this and the neighbouring provinces." This decision, however, does not appear to have been made public; and Thompson, on his release, retired to Charlestown, near Boston. When the buildings of Harvard College were converted into barracks, Major Thompson assisted in the transfer of the books to Concord. It is said that, after the battle of Charlestown, Thompson was introduced to General Washington, and would probably have received a commission under him but for the opposition of some of the New Hampshire officers. He afterwards took refuge in Boston, and it does not appear that he ever again saw his wife or her father. His daughter he did not see again till 1796, when she was twenty-two years of age. On March 24, 1776, General Washington obliged the British troops to evacuate Boston; Thompson was the first official bearer of this intelligence to London. Of course, his property at Concord was confiscated to the commonwealth of Massachusetts, and he himself was proscribed in the Alienation Act of New Hampshire, in 1778.

When Thompson reached London with the intelligence of the evacuation of Boston, Lord George Germaine, the Secretary for War, saw that he could afford much information which would be of value to the Government. An appointment was soon found for him in the Colonial Office, and afterwards he was made Secretary of the Province of Georgia, in which latter capacity, however, he had no duties to fulfil. Throughout his career in the Colonial Office he remained on very intimate terms with Lord George Germaine, and generally breakfasted with him. In July, 1778, he was guest of Lord George at Stoneland Lodge, and here, in company with Mr. Ball, the Rector of Withyham, he undertook experiments "to determine the most advantageous situation for the vent in firearms, and to measure the velocities of bullets and the recoil under various circumstances."

The results of these investigations procured for him the friendship of Sir Joseph Banks, the President of the Royal Society, and Thompson was not the man to lose opportunities for want of making use of them. In 1779 he was elected a Fellow of the Royal Society, "as a gentleman well versed in natural knowledge and many branches of polite learning." In the same year he went for a cruise in the Victory with Sir Charles Hardy, in order to pursue his experiments on gunpowder with heavy guns. Here he studied the principles of naval artillery, and devised a new code of marine signals. In 1780 he was made Under-Secretary of State for the Northern Department, and in that capacity had the oversight of the transport and commissariat arrangements for the British forces.

On the defeat of Cornwallis, Lord George Germaine and his department had to bear the brunt of Parliamentary dissatisfaction. Lord George resigned his position in the Government, and was created Viscount Sackville. He had, however, previously conferred on Thompson a commission as lieutenant-colonel in the British army, and Thompson, probably foreseeing the outcome of events and its effect on the Ministry, was already in America when Lord George resigned. He had intended landing at New York, but contrary winds drove him to Charlestown. It is needless to trace the sad events which preceded the end of the war. It was to be expected that many bitter statements would be made by his countrymen respecting Thompson's own actions as colonel commanding a British garrison, for at length he succeeded in reaching Long Island, and taking the command of the King's American Dragoons, who were there awaiting him. The spirit of war always acts injuriously on those exposed to its influence, and Lieutenant-Colonel Thompson in Long Island was doubtless a very different man from that which we find him to have been before and after; nor were the months so spent very fruitful in scientific work.

In 1783, before the final disbanding of the British forces, Thompson returned to England, and was promoted to the rank of colonel, with half-pay for the rest of his life. Still anxious for military service, he obtained permission to travel on the Continent, in hopes of serving in the Austrian army against the Turks. He took with him three English horses, which rendered themselves very objectionable to his fellow-travellers while crossing the Channel in a small boat. Thompson went to Strasbourg, where he attracted the attention of the Prince Maximilian, then Field-Marshal of France, but afterwards Elector of Bavaria. On leaving Strasbourg, the prince gave him an introduction to his uncle, the Elector of Bavaria. He stayed some days at Munich, but on reaching Vienna learned that the war against the Turks would not be carried on, so he returned to Munich, and thence to England.

M. Pictet gives the following as Rumford's account of the manner in which he was cured of his passion for war: —

"'I owe it,' said he to me, one day, 'to a beneficent Deity, that I was cured in season of this martial folly. I met, at the house of the Prince de Kaunitz, a lady, aged seventy years, of infinite spirit and full of information. She was the wife of General Bourghausen. The emperor, Joseph II., came often to pass the evening with her. This excellent person conceived a regard for me; she gave me the wisest advice, made my ideas take a new direction, and opened my eyes to other kinds of glory than that of victory in battle.'"

If the course in life which Colonel Thompson afterwards took was due to the advice of this lady, she deserves a European reputation. The Elector of Bavaria, Charles Theodore, gave Thompson a pressing invitation to enter his service in a sort of semi-military and semi-civil capacity, to assist in reorganizing his dominions and removing the abuses which had crept in. Before accepting this appointment, it was necessary to obtain the permission of George III. The king not only approved of the arrangement, but on February 23, 1784, conferred on the colonel the honour of knighthood. Sir Benjamin then returned to Bavaria, and was appointed by the elector colonel of a regiment of cavalry and general aide-de-camp. A palatial residence in Munich was furnished for him, and here he lived more as a prince than a soldier. It was eleven years before he returned, even on a visit, to England, and these years were spent by him in works of philanthropy and statesmanship, to which it is difficult to find a parallel. At one time he is found reorganizing the military system of the country, arranging a complete system of military police, erecting arsenals at Mannheim and Munich; at another time he is carrying out scientific investigations in one of these arsenals; and then he is cooking cheap dinners for the poor of the country.