Nature's Teachings

The Siren is even brought into the service of entomologists, enabling them to measure by the sound the rapidity with which a flying insect moves its wings. By means of this instrument we know the origin of the sharp, piercing “ping” of the Gnat, and the heavy, dull boom of the Humble-bee, both of which insects are given in the illustration.

Before taking leave of this subject, I may mention that the instrument is called the Siren because it sings as well under water as in the air, provided that water instead of air be driven through it.

Echo

Our last page will be given to the phenomenon called by the name of Echo, which consists in the power of solid substances, whether natural or artificial, of reflecting the waves of sound thrown against them, just as a mirror reflects the waves of light.

Very often the Echo is naturally formed, as shown in the illustration, by rocks which cast back the sound—waves thrown against them. This is the case in several parts of Dovedale in Derbyshire, where a pistol shot is reverberated backwards and forwards in a most wonderful manner, and a trumpet blast repeats itself over and over again.

At Walton Hall, the residence of the late C. Waterton, Esq., there is a wonderful Echo, nearly half a mile from the house. Mr. Waterton had discovered the Echo, which proceeded from the walls of the house, and, having found its focus, placed on it a large stone, called the Echo-stone. Any one sitting on this stone, and singing, speaking, or whistling towards the house, heard every sound repeated, as if in mockery.

The celebrated Whispering Gallery in St. Paul’s Cathedral is nothing but an ordinary Echo, though so intensified by the process of radiation, that the sound is transmitted from one side of the dome to the other, just as light or heat is reflected from concave mirrors.

1

By sailors the Velella is popularly known by the name of “Sally-man;” i.e. Sallee-man.

2

Now Sir Henry J. Burford Hancock, Chief Justice of Gibraltar.