Chemistry and Physics. 465 



■ the tube; and then the open 

 end was carefully closed by fusion at a glass-blower's lamp. 

 Four tubes thus prepared umh rw< nt a double w. ighing : and then, 

 by inclining the tubes, the sulphuric acid was brought into con- 

 tact with the zinc. The pressure .>:' tlie hydrogen was shown by 

 the diminution of volume of the air in the capillary tube, which 

 ser\ed lor a manometer. Its amount on the iirst day. in the 

 i idies, was from 1^ to 10 atmospheres, rose in rive months 

 up to 27-54 atmosphere and in 17 years up to '25-120 atmospheres. 

 lis time the tubes were frequently doubly weighed on an 

 : i 

 0-3 of a milbgrim, \\a^ always found. 



Another similar tube, with carbonate of lime and concentrated 

 sulphuric acid, in which the pressure of the carbonic acid gas 

 amounted on the first day to 21 atmospheres, after five months to 

 •'.4 aim. spheres, and after 17 years to 44, showed likewise always 

 the same weight of 14-6361 grams. 



Thus according to these experiments, a pressure of from 40 to 

 100 atmosphere- canm t, during a space of seventeen years, force 

 through l'-:> mm. thickness of glass a perceptible quantity of 

 hydrogen ,,]■ carbonic acid. 



While at the commencement the concentrated sulphuric acid 



wetted, the glass sides of the tube, and showed a sharp marginal 



angle (apparently " >. gradually in the course of years the angle 



condensed 



carl onii acid lik< qui ksilvei i i a glass t i> t till* i with air. 



In the at u ' < angh arte margin of the 



irk aid, which at first likewise wetted the sides, has 

 also increased to about 60°. 



The glass thus appears to have gradually in the course of years, 



under the influence of the great pressure, become coated with a 



thin lav. r ..fear' -.i w acid > r I ydrogen n-pccth t :y. which exerts 



attraction from that which glass exert- upon the 



Houid ]. articles at the margin of the surface. A -i 



gas must have been deposited on_ the surface uf the zinc and 



obstructed the further chemical action of the acid.— Pogg. Ann., 



clx, 118; Phil. Mag., iii, 3 1 4. e. « ■. p. 



12. Polar iz<itU,n ft) !:■<■■ '■■ >r.—\\. J. ]> .-ham xphm - the 



ight &**" 



i ,p it m uig • t I" . vial. t 

 nation is about 37°. The ratio of I 

 red rays is consequent ■>"" : V*- 



Xicol is rotated fm°. If the it;.';. 



\/-j= 1-414 the p.-larization would be complete. Calculation 

 shows that for oil of cassia the ratio of the red rays is 6-3 and of 

 the violet _-s. F rmiug a rainbow l.\ -, it tu _ this liquid m 

 sunlight by an atomizer the light cannot be extinguished by a 

 Nicol prism in any position. — Pogg. Ann., clx, 123. e. c. p. 



