Intelligence and Miscellaneous ArticDni 405^ 



We'arfi' therefore able artificially to reproduce hydrophone, this 

 rare variety of quartz, and the curious property of which had struck 

 itt^neralogists. .,i,^ . ^ , , , , .j^ .^^ j^;^ yjj 



A Very small proportion of foreign substances suffices m fact- to 

 modify the translucidity and the appearance of the hydrate of silicac 

 thus a small flask containing silicic aether having been closed by mjsr 

 tajce with a cork, which belonged to a bottle full of creosote, tQjBj 

 aether, on becoming coagulated under the action of moi^it air, yielded! 

 a slightly yellowish silica, and merely translucid like chalcedony : 

 the product thus obtained was not hydrophanous. • , 



I propose to continue and to vary these experiments, which appear 

 to me of great importance and of considerable interest.— Conwiei 

 Re7idus, iSept. 1. , /, a 



sdJ tit ti9§'{xo lioutii 8X3 001 , il// .ejBibvd b ei Jl .VT'I 



^(Oi8) ^fi„3uf«»^^??:fli|^NTS IN vnoxo.^J>j^^ .^^^ ni bb jsoilia 



To the Editors of the Philosophical Magazine and Journal. .OH 



ho-titefgj^^i]gtt^JfTniT ;, ,., .,<.K^o ni JjsiJnsaao ei ll 



^'ifi'rom the many able papers which occasiori^^''j^U^.^^'^a^ 

 Journal on photography, by Sir J. Herschel, Messrs. l^ttof/Hmifc 

 and others, I am induced' to believe that any facts bearing on that 

 most interesting subject will be welcome. I therefore hasten tli' 

 communicate them for the information of your numerous readers. ''^*' 

 My attention has lately been directed to ascertain what other sttlii' 

 stances besides chlorine and bromine, separately and combined, pds-^ 

 sessed the property of accelerating the action of light on a DagueV- 

 rean or iodized plate ; and after many trials, I found that the vapoiiS 

 of ammonia possesses this singular quality in a very remarkable ^^ 

 gree. I first employed it with iodine alone, by simply iodizing a plate 

 to a full yellow colour, and then exposed it for a few seconds to the 

 vapour of ammonia in an exceedingly attenuated state by adding a few^ 

 drops of strong ammonia to a little water, just sufficient to recognisS' 

 it by its odour ; thus prepared it was placed in the camera, and pro- 

 duced a perfect impression of a building in half a minute in mode- 

 rate sunshine ; and several other experiments satisfied me that am- 

 moniacal vapour has a very quickening action on. iodine alone. My 

 next step was to ascertain how it would operate with bromine ; exJv 

 pecting it would either destroy or accelerate its action, I was reite 

 joiced to find that it had the latter effect, and that plates prepared in 

 the usual manner, with iodine and simple bromine water, are ren- 

 dered infinitely more sensitive by exposing them a few seconds to 

 this vapour than they are without it. Having found that I could ob- 

 tain a perfect impression in sunshine instantaneously, and that five 

 or ten seconds only were sufficient in a moderate light, I indulge the 

 hope that, with its assistance, moving objects may therefore be 

 taken with facility. I should inform you that I have employed thia 

 substance in a variety of shapes, by exposing the plates to its influii 

 ence previous to placing them in the camera, or by allowing it to be? 

 evolved in it during the operation, or just before it is used, and in 

 each case have found it eq^ually efficacious. What is remarkable 



