496 
PHYSICS: C. BARUS 
Proc. N. a. S. 
2. Apparatus. — The chief difficulty with the experiment at the outset 
seems to be the eHmination of loss of gas by diffusion. This, in the case of 
a cylindrical diver, open below, amounted in the experiments cited, to 
0.41% per day. It would not, therefore, be long before the whole of the 
gas would be lost. To avoid this, two resources suggest themselves: 
(1) to place the diver about midway between two layers of air, one below 
and the other above it; and (2) to provide the diver with a long slender 
neck below, precisely what was to be avoided in cases of diffusion. I 
shall not describe the forms of apparatus in which the first precautions 
were taken, as they proved to be unavailable; nor any of the correlative 
forms with the diver sheathed within a completely submerged cylindrical 
tube, nearly closed. The results so obtained were no better than those 
FIGS. 1 AND 2 
found with the extremely simple apparatus, figure 1 . The swimmer being 
her^ lighter than water, AA is the standglass, wholly filled and a, b, the 
swimmer held down at a definite level by the thermometer T. M is 
a water manometer for registering the pressure excess at which flota- 
tion just occurs at the given level. Pressure is applied by aid of the small 
water reservoir, R, communicating with A A by the tube t with the stop- 
cock F, and the flexible pipe py the whole system t F p R being full of 
water. To make an observation, R is raised sufficiently and clamped. 
The cock F, is now slightly opened, until the swimmer just begins to sink. 
The head of water, h, is then read off at M. This adjustment may be 
made to a fraction of a millimeter of water. The apparatus admits of 
observation in an agitated environment. 
The diver, which to be sensitive must be as light as possible (thin stem 
preferable), consisted of a bulb 4.5 cm. in diameter and a stem 4 cm. 
long and about 2 mm. in diameter. The rate of loss would be decreased 
