480 WRITINGS OF JOSEPH HENRY. fl875 



is less elevating power in a fine tube) had sometimes greater 

 power in ascending in the meshes of a wick. 



The relative fluidity of the different oils was obtained by 

 filling with them in succession — a pear-shaped vessel of about 

 the capacity of a pint, with a narrow neck, and having a hole 

 in the lowest part of the bottom of about a tenth of an inch 

 in diameter. Such a vessel filled with any number of perfect 

 liquids would be emptied in the same time, whatever their 

 specific gravity. As at any given horizon inertia is directly 

 proportional to gravity, the heavier the liquid the greater 

 would be the power required to move it ; but the motive power 

 would be in proportion to the pressure, or in other words to 

 the weight, and therefore all perfect liquids should issue from 

 the same orifice with the same velocity. To test this propo- 

 sition, eight fluid ounces of clean mercury, and then the 

 same bulk of distilled water, were allowed to run out of the 

 vessel above mentioned; the time observed was the same 

 within the nearest second. It was found in repeating this 

 experiment with sperm and lard oils that the rapidity of the 

 flow of the former exceeded considerably that of the latter, 

 the ratio of time being 100 to 167. 



The results thus far in these investigations were appar- 

 ently against the use of lard oil; it was observed however in 

 the experiments on the flow of the two oils on different occa- 

 sions that a variation in the time occurred, which could be 

 attributed only to a variation in the temperatures at which 

 the experiments were made. In relation to this point, the 

 effect of an increase of the temperature above that of the 

 atmosphere — on the flowing of the two oils, was observed. 

 By this means the important fact was elicited that as the 

 temperature was increased, the liquidity of the lard oil in- 

 creased in a more rapid degree than that of the sperm oil, 

 and that at the temperature of about 250° F. the liquidity of 

 the former exceeded that of the latter. 



A similar series of experiments was made in regard to the 

 rapidity of ascent of the oil in the wick, and with a similar 

 result. At about the temperature just above mentioned, 

 the ascensional power of the lard oil was greater than that of 



