Photographic Processes. 233 



The desire for escaping appears to be a constant habitude 

 of the natterjack, and its powers both of burrowing and 

 climbing cause it to rival Baron Trenck in the success of its 

 endeavours. Mr. Andrews kept some specimens for years in 

 his garden at Rathmines, near Dublin, and has observed that 

 nothing but high walls, with deeply laid foundations, will avail 

 to secure them. Three or four natterjacks will assist three or 

 four more to climb by generously allowing their shoulders to 

 be used as ladders : these creatures piling themselves one on 

 another, like Chinese tumblers, and actively holding on to the 

 smallest inequalities of the wall. 



Mr. Townsend concludes his letter by repeating the legen- 

 dary story of St. Patrick, which he gives to nearly the same effect 

 as Mr. Andrews did, adding, however, that the persons who 

 told it to him had no idea that toads inhabited their neigh- 

 bourhood. But, surely, we need not complain of the excep- 

 tions which present themselves to the non-existence of reptiles 

 in this Green Isle. If the word of promise in this matter be 

 broken to the ear, surely it is fulfilled to the hope ; we have 

 no colony of snakes, no lurking adders, although we now and 

 then meet with the sand lizard ; are plentifully supplied with 

 the frog and smooth-newt, and possess in Kerry — and pos- 

 sibly elsewhere in Ireland — an isolated party of the harmless 

 Natterjack Toad. 



PHOTOGRAPHIC PROCESSES.* 



BY J. W. M f GAULEY. 



It is not our purpose to enter into the minor details of photo- 

 graphy ; we shall content ourselves with noticing the character- 

 istic features of the various processes, remarking, once for 

 all, that each of them may be modified in a great variety of 

 ways. 



The Daguerreotype Process. A silver plate of the required 

 size, having been most carefully cleaned, is iodized, or bromo- 

 iodized, by the exposure of its silvered surface to the vapour 

 of iodine, or of iodine and bromine ; it thus acquires a golden 

 colour. Having been then placed in the camera and exposed 

 to light for a length of time, varying with the state of the 

 atmosphere, it is submitted to the action of the vapour of 

 mercury, which brings out a picture that was before invisible. 

 The silver salts which have not been decomposed by the action 



* This is the second article of a series. The first, on The History of 

 Photography, appeared in No. 27, April, 1864. The third and concluding 

 paper will be given at an early date. 



