68 J. Waterhouse — Photography in connection with [No. 2, 



spared from my regular office duties was devoted to preliminary trials of 

 dry plates in Calcutta till October, when I joined Colonel Tennant at 

 Roorkee. 



It was understood that the English observers were to use the beer-al- 

 bumen dry process recommended by Captain Abney, R. E., and therefore 

 my first trials were with it ; but although the instructions given by Captain 

 Abney were carefully carried out, it was found impossible to obtain the 

 exalted sensitiveness claimed for the plates and, though the pictures obtain- 

 ed had many good qualities, the exposures were so long that I could not 

 but consider the process unsuitable and look for some other by which 

 more sensitive plates could be secured. The beer-albumen process was, 

 however, tried on several different occasions, both in Calcutta and at Roor- 

 kee, with different collodions and various samples of beer, but always with 

 the same result. 



The cause of the great want of sensitiveness shewn by these plates 

 could not be discovered. Captain Abney says that those who have not 

 succeeded with his process have not used a sufficiently porous collodion ; but 

 on this occasion several collodions were used, some containing a large pro- 

 portion of water, but without any noticeable advantage ; though other dry 

 plates taken with the same collodions gave much greater sensitiveness.* 



It is possible that the beer used was not quite suitable from containing 

 too large a quantiby of chlorides or other substances detrimental to sensi- 

 tiveness, and that this was probably the case is shown by the fact that a 

 much greater sensitiveness and generally better results were obtained with 

 the mode of working the beer-albumen process recommended by Mr. 

 Davies of Edinburgh, in which a small quantity of nitrate of silver is 

 added to the beer with the effect of throwing down all the chlorides and 

 much of a glutinous substance ; but even this modification did not give 

 quite satisfactory results and the idea of using the beer-albumen process 

 for the Transit plates was given up. Although the process has no doubt 

 yielded excellent results in the skilled hands of Captain Abney and others, 

 the uncertain composition of the different liquids known as beer render it 

 undesirable that this substance should be used in the preparation of dry 

 plates which are to serve as a standard for scientific purposes and from which 

 comparable results are expected. Eor such purposes more certainty and 



* I have quite recently tried the beer-albumen process again with samples of collo- 

 dion yielding good results with other dry processes — but found the plates just as in- 

 sensitive as they were before. By flowing the films, after washing away the free 

 silver, with a 10-grain solution of pyrogallic acid in beer, then again well washing, 

 and finally flowing the plate with a mixture of glycerine and dilute albumen, plates 

 were obtained giving excellent results with at least ten times more sensitiveness than 

 those prepared by Captain Abney' s plan. 



