Intelligence and Miscellaneous Articles, 505 



of cavities. Durocher is of opinion, that the assumption of some 

 geologists, that dolomite has been formed naturally by aqueous 

 agency, is proved by this experiment not to be absolutely correct, as 

 it may also have been formed by magnesian vapours issuing from the 

 interior of the earth, and gradually converting limestone into dolo- 

 mite. — Comptes Rendus, vol. xxxiii. p. 64. . ^^j,-^ ,^ U/li bJO'jS' 



NEW PHOTOGRAPHIC PROCESS UPON GLASS. 

 BY M. J. R. LE MOYNE. 



The process in question is completely practical, and does not 

 merely refer to a few accidental occurrences. Nearly a year ago, I 

 found that the impressions upon glass sometimes presented a posi- 

 tive aspect, and after a short period, my researches in this direction 

 furnished me with tolerably good specimens ; but I did not succeed 

 in arriving at a sure and constant method until after making a long 

 series of continuous attempts ; these have extended to the present 

 time. 



The object of most of my experiments was to overcome the well- 

 known inconveniences of the albuminous plates, and, independently 

 of the positive process, I have made considerable progress in the 

 production of the impressions by the following modifications, which 

 in fact constitute a new method of preparation : — 



1. Purification of the albumen of the whites of eggs by keeping 

 them for a long time, and even adding sugar to produce slight fer- 

 mentation, which clarifies them much better than the beating process 

 which is generally adopted. This first addition of sugar (8 grs. to 

 each white of egg) does not prevent the necessity of subsequently 

 adding the quantity already recommended (38 to 46 grs.) to obtain 

 greater sensibility to light; and with the processes I afterwards 

 employ, the presence of this substance increases the adhesion of the 

 coating, instead of diminishing it, which has been urged as an ob- 

 jection to it. 



2. Iodizing the albuminous part, after it has dried, by immersing 

 it in a bath of tincture of iodine to which yo^h part of its volume of 

 nitric acid of specific gravity I'SSO has been added. 



This method is very simple, and is not attended with any of the 

 defects inherent to the use of albumen containing iodide of potassium 

 in solution. There is but one of the processes known which could 

 be brought into competition with this ; it is the employment of the 

 vapour of iodine ; but the moist method has the advantage, both in 

 the rapidity of execution and in the simplicity of the apparatus. 



3. Omission of the use of acetic acid, and employing a simple 

 solution of nitrate of silver (1 part to 10), for rendering the plates 

 sensible. 



I do not know whether acetic acid is really necessary, upon albu- 

 minated glass, when gallic acid is used to bring out the image ; but, 

 with the sulphate of iron, it is undoubtedly an expensive superfluity; 

 moreover, the volatility of this acid is a cause of spontaneous 

 changes in the solutions, and this is also a serious inconvenience. 



