JOUENAL 



OF THE 



ROYAL MICROSCOPICAL SOCIETY, 



AUGUST, 1909 



TRANSACTIONS OF THE SOCIETY. 



XII. — A New Illuminator for the Microscope. 

 By J. W. Gordon, F.R.M.S. 



(Read May 19, 1909.) 



In bringing before the Society the speculum illuminator which is 

 on the table this evening, I feel that I owe an apology to Dr. 

 Spitta. A few months ago he requested me to supply him, for the 

 purposes of the second edition of his book, with a drawing of my 

 new apparatus. I did so, giving him a drawing which showed all 

 the improvements at that time devised. Subsequent work with 

 that form of the illuminator, however, has satisfied me that it was 

 so very unhandy that I cannot now explain the still further 

 improved form, which this evening I have the honour of submit- 

 ting to the Society, without, at least by inference, criticising with 

 some severity the design furnished to Dr. Spitta. In these circum- 

 stances I should, if I felt any responsibility for what has occurred, 

 be thoroughly ashamed of myself ; but, in fact, I did my best at 

 the time, not being then aware how serious were the shortcomings 

 of that model, and not having any idea of the newer improve- 

 ments, which have, as I hope, made the model now submitted 

 very much handier in use. 



In principle the illuminator is the same — that is to say, it 

 consists of a speculum having a ground-glass end turned towards 

 the actual source of light. The importance of this ground-glass 

 screen has been already pointed out to the Society. It enables us 

 to make use of what is otherwise an impossible, though, when 

 rendered possible, an extremely convenient, source of light — that 

 is to say, the incandescent filament of an electric lamp. I have 

 on previous occasions shown a glass speculum illuminated by means 



Aug. 18th, 1909 2 f 



