112 PROCEEDINGS OF SOCIETIES. 



cavities to fit the feet of tlie micros cope ; next a stand to support the 

 condenser and alum cell ; finally a mirror moveable in all directions, 

 the motion being performed by means of pulleys at the back of 

 the instrument. The ( amera is connected with the microscope 

 by means of a loosely-fitting metal tube, made proof against light 

 by a lining of thick washleather. The instrument is used by 

 placing it across a table in front of a window, so that the mirror 

 projects out of it clear of all shadow. The condenser is focussed 

 by sliding it along the tramway, the light thrown on by pulling 

 with the string, and the exposure conducted as in all photographic 

 manipulations, the time of exposure being as instantaneous as 

 possible. 



The process that answers best when the sun is tolerably 

 constant is the ordinary "wet collodion;" but when it is being 

 often obscured by clouds the " gelatin-bromide," in the form of 

 " Kenuet's patent sensitised gelatin-pellicle," a dry process, and 

 by which micro-photographs can be obtained by the light of an 

 ordinary paraffin lamp. 



The Chairman suggested the use of a frosted silver mirror to 

 supply a white light. 



Dr. Matthews proposed using a paraffin lamp with double 

 flame, and stated that, in order to save daylight, plates need not 

 be developed at once, but could be put aside safely for some 

 hours if melted with treacle and water. The yellow colour of 

 the specimens, if it were requisite, might be corrected with 

 hsematoxylin. 



Mr. Giles, in reply, preferred sunlight direct if it could be 

 obtained, and did not find the colour of the slides any drawback. 



Differential Warm Stage.- — Mr. Golding-Bird explained and ex- 

 hibited in action a simple form of hot stage, heated by a spirit 

 lamp, capable of being kept in action for any length of time, its 

 temperature being regulated according to the condition of pieces 

 of solid paraffin placed on it, and on a copper tongue connected 

 with it. He had found it extremely useful for purposes of de- 

 monstration, and its simplicity allowed of its being used in the 

 wards of an hospital when examining blood in a morbid state.^ 



A discussion followed, and the meeting then resolved itself 

 into a conversazione. 



' This stage has been already described in ' Quarterly Microscopical 

 Journal ' for Oct., 1875, and is made by Millikin, of St. Thomas's Street, 

 Southwark, S.E. 



