152 Proceedings. 



movement ; some advocated eight inches, and some so 

 much as twenty-four. Mr. Dancer was convinced that the 

 proper separation was the ordinary distance between the 

 eyes of a human being, and made his camera under this 

 idea ; from that time no other form of camera has been 

 used. 



Omitting several other instruments which Mr. Dancer 

 improved, mention must be made of his connection with Dr. 

 Joule in his heat experiments and discoveries. Dr. Joule 

 found the necessity for accurate thermometers, and with 

 Mr. Dancer's assistance determined to make them for 

 himself The result was the production of a new 

 thermometer, the first made in England with any preten- 

 tions to accuracy. Mr. Dancer arranged the apparatus for 

 measuring the internal capacity of the bore of the 

 thermometer tubes, and constructed for Dr. Joule the 

 apparatus which he employed in his determination of the 

 mechanical equivalent of heat, also a tangent galvanometer 

 and other original instruments. 



When Mr. Dancer established himself as an optician in 

 Manchester, his presence soon made itself felt amongst the 

 few microscopists then living in the district. Good micro- 

 scopes were then costly, and worthless ones very common. 

 Mr. Dancer successively brought out several forms of in- 

 struments, as excellent in their mechanical and optical 

 arrangements as they were moderate in price. Instruments 

 fully equal to the requirements of original research were 

 thus brought within the reach of many whose observing 

 faculties were more conspicuous than their financial 

 resources. It would be difficult to over-estimate the 

 stimulus which Mr. Dancer thus gave to Manchester micro- 

 scopy ; it cannot be doubted that the present energy of 

 our local microscopists is the direct outcome of the impulse 

 which their means of research then received. 



Latterly Mr. Dancer lost his most precious possession — 



