Page:Passages from the Life of a Philosopher.djvu/226

210 pain is felt in the ears; but it now arises from the dense air which had filled them endeavouring, as the pressure is removed, to force its way out.

If the water is clear, and not much disturbed, the light in the bell is very considerable; and, even at the depth of twenty feet, was more than is usual in many sitting-rooms. Within the distance of eight or ten feet, the stones at the bottom began to be visible. The pain in the ears still continues to occur at intervals, until the descent of the bell terminates by its resting on the ground. The light is sufficient, after passing through twenty feet of sea water, even for delicate experiments; and a far less quantity is enough for the work which is usually performed in those situations.

The temperatures of the hand and of the mouth, under the tongue, were measured by a thermometer, but they did not seem to differ from those which had been determined by the same instrument previous to the descent; at least, the difference did not amount to one-sixth of a degree of Fahrenheit's scale. The pulse was more frequent.

A small magnetic needle did not appear to have entirely lost its directive power, when placed on the footboard in the middle of the bell; but its direction was not the same as that which it indicated on shore. This was determined by directing, by means of signals, the workmen above to move the bell in the direction of one of the co-ordinates; a stick then being pressed against the bottom drew a line parallel to that co-ordinate, its direction by compass was ascertained in the bell, and the direction of the co-ordinate was determined on returning to the surface after leaving the bell.

Signals are communicated by the workmen in the bell to those above, by striking against the side of the bell with a hammer. Those most frequently wanted are indicated by