DR. R. M. WALMSLEY, LT.-COL. GIFFORD 87 



men for that work. I take that to be an absolute condition if we 

 are to turn out instruments of high precision of this nature in quan- 

 tity. The key of the situation lies in the inspection room of the 

 factory, and unless the inspection room is adequately staffed with 

 thoroughly trained men, the microscope manufacturers of this country 

 cannot hope to rival what has been done — to which I refer with 

 some diffidence in the presence of the President — in the engineering 

 industry. Every engineer knows that the production of apparatus 

 and machinery by the engineering industiy — high-speed steam engines 

 and things like that — has been due to efficient inspection by highly 

 trained men in the inspection department. Parts are made in quan- 

 tity, and are interchangeable, and the thing to aim at is to take 

 the parts from store and have them fitted together without further 

 adjustment by skilled workmen, and so to produce the finished 

 article or machine. If the inspection department does its duty, we 

 need not fear the competition of America or of France, both of 

 which will be more serious than that of Germany in the near future; 

 we need not fear it at all. The British microscope will then stand 

 before the world and hold its own. 



Lieut. =Colone! Gifford : In my experience I have worked out a 

 good many apochromatic combinations, chiefly for telescopes, but I 

 have never found any three glasses which gave a sufficiently long 

 focus for microscopic objectives. That has led me to believe that 

 the so-called apochromatic objectives for microscopes, excellent as 

 they are, are not true apochromatics ; I mean lenses which combine 

 foci for three different portions of the spectrum. Whether that is 

 so or not, I do not know, but I have met many people who know 

 something of the subject who confirm me in this opinion. 



Instructor=Commander M. A. Ainslie : This matter of the apo- 

 chromatic objective has been occupying my attention for about 12 

 years, mainly from the point of view of what they would do in the 

 resolution of very fine structure, and from the point of view of 

 comparison between different types of objective. What put it into 

 my mind to address the meeting was the fact that Mr. Swift just 

 now was referring to his own objective. Mr. Swift a year or two 

 ago was good enough to send me two 4 mm. objectives, one of which 

 was entirely the equal of a perfect Zeiss 4 mm. ; and I have some 

 knowledge of Zeiss 4 mm. objectives, because I have used 18 of 

 them on the same specimen, and I know that specimen by heart. 

 One of the objectives sent me by Mr. Swift was fully equal to any- 

 thing that Zeiss had done, but the other one was not. I presume 

 that our English opticians are working, so to speak, to a standard. 

 I know that they can turn out work which is in every way as good 

 as anything that has ever been turned out in other countries ; but 

 while Continental opticians seem to have a habit of turning ,out 

 what I might call objectives of 80 to 85 per cent, perfection, our 

 English opticians seem sometimes to turn out something which is 

 very fine — 95 per cent. — but they often also turn out something 

 which is about 60 per cent, perfection. In my experience in an 

 amateur way, I have tested a very large number of immersion objec- 

 tives, and of dry objectives with apertures from .4 to .95. I am 



