534 Sir David Salomons [Feb. 26, 



WEEKLY EVENING MEETING, 



Friday, February 26, 1892. 



Sir Frederick Bramwell, Bart. D.C.L. F.E.S. Honorary Secretary 

 and Vice-President, in the Chair. 



Sir David Salomons, Bart. M.A. M.B.I. 



Optical Projection. 



The intention of this lecture is to give a general survey of the 

 subject of Optical Projection, which now takes its position in science, 

 and to present examples of what may be done by this method. It 

 would be difficult to determine which subject claims a first place. 

 Some scientists say the microscope should have the preference, while 

 others take a different view. For my own part, I think the microscope 

 and polariscope stand foremost, on account of the facility with which 

 these branches of science may be pursued for the benefit of a large 

 number, without multiplying expensive apparatus ; also because of 

 the convenience in saving the eyes from undue strain. Indeed, to 

 many persons, looking at objects in the table microscope is little 

 short of a painful operation, and consequently the study of small 

 objects becomes to them impossible. The projection method immedi- 

 ately brings the required relief. 



For general instruction, projection methods are invaluable, such as 

 for instance, showing diagrams, photographs, and other slides, upon 

 the screen ; as well as for spectrum analysis. In fact, the subjects 

 which can be illustrated by means of optical projection are in- 

 numerable ; but time will allow me to present only a few examples, 

 and I trust that, when I approach the end of my lecture, my view 

 of the importance of this subject will be held in equal estimation 

 by you. 



Probably the only people in the world that benefit by the ex- 

 perience of their predecessors are those who pursue the study of 

 science. They are free from the accusation of robbing the brains of 

 other men, when they take up methods or apparatus already known 

 and improve upon them or employ them for their own work. In such 

 eases, however, it is always understood that honour should be given 

 where honour is due, and accordingly I have no wish to represent to 

 you any piece of apparatus as of my own devising, when in reality it 

 belongs to another. 



Few men have had a larger experience, and attained greater 

 success in optical projection, than has Mr. Lewis Wright, who has 

 embodied in his most recent forms of apparatus all that was good in 

 designs existing until his time. I have, therefore, started from his 

 models, making such modifications as I thought to be desirable. 



