Prof. Graham on the Law of the Diffusion of Gases. 269 



the integrals being each taken from v = (x + *l) to v = {x — *1). 

 Computing the intensity for each value of x in this way, I ob- 

 tain the following results. 



Va>"e of,. *ggr Value of, $g£ Value of,. '*gj* 



04 1-0 -0387 2-5 -0324 



•1 -04 1-1 -0384 2-7 -0312 



•2 -0399 1-2 -0381 2-9 -0300 



•3 -0398 1-3 -0378 3-1 0287 



-4 -0397 1-4 -0375 3-3 -0274 



•5 -0396 1-5 -0371 3-5 -0261 



•6 -0395 1-7 -0363 3-7 -0248 



•7 -0393 1-9 -0355 3-9 -0236 



•8 -0391 2-1 -0345 4-3 -0208 



•9 -0389 2-3 -0335 4-7 -0182 



5-1 -0156 



It will be seen that the intensity of the light is a maximum 

 at the centre of the spectrum ; or when x, the distance from 

 that centre, is equal to 0. 



I have supposed a = 30 inches, and b — 21 inches, simply 

 because these appear to have been about the distances of the 

 knives, from the window- shutter and from the paper respec- 

 tively, in Newton's observation. But if any other values are 

 assigned to these latter, provided the interval between the 

 two blades is very small, the same conclusion will be found to 

 hold good. 



I might refer to other phaenomena, which appear to me no 

 less irreconcileable with the undulatory hypothesis than those 

 here considered. But this seems unnecessary ; for if the pre- 

 ceding reasonings and computations involve no error, they are 

 surely of themselves sufficient to overthrow that hypothesis. 



XLIV. On the Law of the Diffusion of Gases. By Thomas 

 Graham, Esq. M.A. F.R.S. Ed., Professor of Chemistry in 

 the Andersonian University, Glasgow. 



[Continued from p. 190.] 



2. Diffusion qf Carbonic Acid Gas. 



r T^HE most satisfactory experiments with carbonic acid gas 

 * were performed by confining it over a solution of com- 

 mon salt, saturated in the cold, which absorbs this gas very 

 slowly, and, instead of the diffusion-instrument with bulb, a 

 long diffusion-tube was found most suitable. 



Experiment 1 . — Thermometer 64° : dew-point 53°. Baro- 

 meter 30*13. Left in diffusion-tube 17 air, and filled up over 

 brine to 197 with carbonic acid gas, which gives 180 carbonic 



