I 



Hayes — On Micropkotographic Methods. 61 



screen, good definition being obtained by using No. 3 aperture in the 

 condenser diaphragm. I have confined my work to these powers as 

 being representative of the objectives chiefly used in ordinary patho- 

 logical investigations. 



The microscope, as also the objectives and achromatic condenser 

 used, are by Powell and Leland, the \" objective being a dry glass 

 of low angle, and, from its possessing considerable penetration, is 

 particularly suitable for photographic work. 



"With regard to the corrections usually described as necessary on 

 account of the want of coincidence of the chemical visual foci, I have 

 not found such corrections necessary. This in the case of the 1" objec- 

 tive is probably an accidental circumstance due to some peculiarity in 

 that particular case by which the glass does not require correction ; 

 but in the case of the ^" I was assured by Mr. Leland, when convers- 

 ing with him on the subject a short time since, that he would not 

 expect that the \ or any higher power would require any correction. 



The only cases in which the oil -lamp can be satisfactorily used, so 

 far as my trials go, is when a low power such as the 1" or V' is em- 

 ployed. In one picture (shown) which was done in this way, and re- 

 quired five minutes exposure, the result is excellent. 



Wishing to get the colour of the stained specimens on paper, in 

 order to give an appearance as near as possible to that seen in the 

 microscope, I applied to the Woodbury Company to make me some 

 pictures by their gelatine process, employing gelatine coloured to re- 

 present carmine and logwood stains ; they have succeeded admirably, 

 and these prints can be produced in quantity at a very cheap rate- 

 much cheaper than lithographing can be done in Dublin. 



