238 



ADJOURNED DISCUSSION IN LONDON 



in my opinion English manufacturers have always overlooked. If 

 you spring at four corners, like a, b, c, d (Fig. 4), the fitting E 

 has got to) be a very fine fit, and also the fitting F, but directly you 

 start springing E you distort F at once. I have seen it; l" have 

 spent hours over it worrying about it, but English makers are 



Fic.Z 



Fig. 3 



Fig. I 



.E^^=MI|3, 



Fig. 4 



Fig 5 



gradually waking up to the fact that you have got to have your 

 slides in a springless chunk of metal, something like that shown 

 in Fig. 5, so that when you do the screws up, the chunk of metal 

 remains as it was and does not distort. Again, how can you effi- 

 ciently remove the grinding material from the springing slots, which 

 is another obvious source of wear. 



Mr. Beck : Was the microscope 20 years old which you referred 

 to German or English? 



Mr. Perkins: It was German. I am not saying that I have 

 not seen an equally good English instrument 20 years old, but I 

 am speaking of English instruments as a body. Another point is 

 that English makers must now see to it that they have an efficient 

 system of inspection. The Germans have a very efficient system of 

 inspection, and English makers must see that nothing leaves their 

 factories which is not perfect. When you have got to that point, 

 but not before, then success is assured. 



Mr. Harold Wrighton : It fell to my lot to prepare the photo- 

 micrographs which were shown in the paper given by Sir Kobert 

 Iladfield and Mr. T. G. Elliot at the Symposium. These photographs 

 were taken on a Zeiss-Martens horizontal machine. In order to 

 obtain them I found it necessary to alter radically the long distance 

 fine focussing adjustment. Even in the best patterns of photomicro- 

 graphic apparatus the design and efficiency of this long distance 

 focussing fittings seems to receive very little attention. Possibly a 

 description of the new arrangement may be of interest to some 

 gentlemen who have a similar Zeiss-Martens outfit. 



