﻿Miscellanies. 217 



as soon as the mouth is removed, the bubble will be seen to diminish 

 rapidly, and at the same time quite a forcible current of air will be 

 blown through the tube against the face. This effect is not due to the 

 ascent of the heated air from the lungs, with which the bubble was in- 

 flated, for the same effect is produced by inflating with cold air, and 

 also when the bubble is held perpendicularly above the face, so that 

 the current is downwards. 



11 Many experiments were made to determine the amount of this force, 

 by blowing a bubble on the larger end of a glass tube in the form of 

 the letter U, and partially filled with water ; the contractile force of the 

 bubble, transmitted through the enclosed air, forced down the water in 

 the larger leg of the tube, and caused it to rise in the smaller. The 

 difference of level observed by means of a microscope, gave the force 



• m 



in grains per square inch, derived from the known pressure of a given 

 height of water. The thickness of the film of soap water which form- 

 ed the envelope of the bubble, was estimated as before by the color 

 exhibited just before bursting. The results of these experiments agree 

 with those of weighing the bubble, in giving a great intensity to the 

 molecular attraction of the liquid ; equal at least to several hundred 

 pounds to the squarp inch. Several other methods were employed to 

 measure the tenacity of the film, the general results of which were the 

 same : the numerical details of these are reserved, however, until the 

 experiments can be repeated with a more delicate balance. 



u The comparative cohesion of pure water and soap water was deter- 

 mined by the weight necessary to detach the same plate from each ; 

 and in all cases the pure water required the greater force. The want 

 of permanency in the bubble of pure water is therefore not due to 

 feeble attraction, but to the perfect mobility of the molecules, which 

 causes the equilibrium, as in the case of the arch, without friction of 

 parts, to be destroyed by the slightest extraneous force. 



" Several other experiments with films of soap water were also de- 

 scribed, which afford striking illustrations of the principles of capillar- 

 ity, and which apparently have an important bearing on the whole sub- 

 ject of cohesion." — Proceedings Am. Phil Soc, No. 30, April, 1844. 



2. Fossil Footmarks found in Strata of the Carhoniferous Series in 

 Westmoreland County, Pennsylvania. — We have received from Dr. Al- 

 fred T. King of Greensburgh, Westmoreland Co. Penn., an important 

 communication, (which came to hand at too late an hour for publi- 

 cation in this number,) in which he announces the discovery of seven 

 distinct and nondescript footmarks, found on a coarse sandstone of the 

 coal measures one hundred and fifty feet beneath the largest coal seam, 

 and nearly eight hundred feet from the surface of the formation. It 



Vol. xlviii, No. 1.— Oct.-Dec. 1844. 28 



