210 On inflammable gaseons Compounds. 



produced by the more intense light of the Voltaic battery, and I 

 placed the tube contnining the mixed gases in a darkened room, 

 within about an incli of the charcoal points connected with an 

 apparatus of one hundred pairs of plates highly charged : upon 

 making the contact, the efTect of the light upon the mixed gases 

 was very remarkable ; fumes of muriatic vapour were instantly 

 produced, the water rose in the tube in consequence of the pro- 

 duction of muriatic acid, and in about five minutes the absorption 

 was entire; but the most curious circumstance was, that in two 

 instances an explosion of the gases took place the moment they 

 felt the impulse of the electric liglit. 



12. As I have in no case been able to produce an analogous 

 effect by any other terrestrial light, however intense, I cannot but 

 consider the phasnomenon as dependent upon some peculiar pro- 

 l^erty belonging to the rays of solar and electric light. 



The lunar rays produce no effect upon mixed chlorine and hy- 

 drogen, nor upon chloride of silver ; neither was the whiteness 

 of the latter in the slightest degree impaired by the most power- 

 ful luminous focus that I could obtain from an olefiant gas flame. 



13. In some experiments connected with the subjects of this 

 communication, 1 have availed myself of a photometric thermo- 

 meter, acting upon the principle of that described by Mr. Leslie, 

 but infinitely more sensible : it is constructed nearVy in the same 

 way as the differential thermometer, but instead of containing air, 

 the balls are filled with the vapour of ether, and the stem contains 

 a column of that liquid ; it thus forms a very delicate differential 

 thermometer. To convert it into a photometer, the upper bulb 

 is covered with a thin coating of India ink, and the lower one with 

 silver or gold leaf; the whole instrument is then placed in a pel- 

 lucid glass tube : when taken out of its case the influence of light 

 is perceived at the instant of exposure, by the falling of the liquid 

 from the blackened to the metallic side ; it is powerfully influ- 

 enced by the flame of a candle at the distance of one foot, and 

 proportionally by other luniinous bodies. 



[To this paper is annexed a drawing of an Argand burner for oil gas 

 upon what Mr. Brande believes to be the most ctconomical construction. It 

 differs from the common gas Argands, in having the top of the cylindei"S 

 joined, not by a flat ')erfuratcd plate, but by two bevilled rims, ascending 

 from the inner and outer tube respectively, and joining each other at nearly 

 a right angle, the sharp angle being taken otFa little on the upper part, so as 

 to make a flat face for the holes. The bevilling of the perforated edge contri- 

 butes greatly to the perfection of the light, as shown in the section. Fig. 1. 

 The diameter of the circle of holes is 0,7 inch, and the holes should not be 

 more than i of an inch in diameter. Consuming at the highest average 

 4000 cubical inches per hour, it gives the light of between eight and nine 

 wax candles of four to the pound. 



What is technically termed a rose burner has six holes of the same di- 

 mensions as those of the Argand ; and when so regulated as to produce a 

 light equal to that of six wax candles, its greatest average consumption of 

 gas amounts to 4800 cubical inches per hour.] 



XXXIII. Re- 



