A NEW T^ESEARCH MICROSCOPE. 

 By Powell Swift. 



We have, in connection with Messrs. R. & J. Beck, been in 

 consultation with Sir Herbert Jackson and Mr. J. E. Barnard 

 concerning the requirements of a better research microscope for 

 all classes of exacting work than has hitherto been made. This 

 consultation has proceeded only so far as to deal with certain impor- 

 tant aspects of the case. We think the advances that are likely 

 to be made in the microscope will be due to constant discussions 

 between the users and the manufacturers of the instruments, and 

 in order that the discussions which have up to the present taken 

 place should be materialised into something definite, we have pre- 

 pared a model embodying the points that have been so far settled 

 and which should form a stepping stone towards further progress. 



Whereas a standard microscope can be produced which may 

 satisfy the requirements of the ordinary worker for a reasonably 

 long period, we do not think that the best type of instrument is 

 likely to remain stationary as long as scientific progress takes place. 



Therefore, in putting before you this stand, although we think 

 it marks a distinct improvement due to the helpful suggestions that 

 we have already received, we must take entire responsibility ourselves 

 for the details, and merely express our thanks for the valuable 

 assistance we have received from Sir Herbert Jackson and Mr. J. E. 

 Barnard, without its being supposed that they can be held respons- 

 ible for an instrument which we have made in order to exhibit at 

 this meeting, without having had time to discuss the final details 

 with them. 



The first point which was considered was rigidity, and, while 

 adopting the general principle of our " Wales " model, with its 

 curved limb and radial means of inclination, the casting had been 

 made with a metal tie of great strength to connect the portion 

 carrying the body with that carrying the stage, so that when moving 

 from the vertical to the horizontal position there should be no 

 alteration in focus, due to the slight torsion which is otherwise 

 produced in the curved limb. 



The body is 2 inches in diameter, so that a photographic lens 

 placed in its interior enables a large field to be obtained and not 

 cut off by the margin of the tube. A rack and pinion drawtube 

 and supplementary sliding drawtube are provided, so that the 

 mechanical tube length can be varied from 140 to 250 mm. The 

 fine adjustment, which is of the twin side rnilled head type, is fitted 

 with IMessrs. Beck's new double lever adjus'tment, providing in this 

 manner two very delicate adjustments, one of which is five times 

 as fine as the other. 



The entire stage is carried on a very massive right angle cradle, 

 and racks up and down, with all its apparatus for metallurgical 

 work having a travel of 2^^ inches. This is more solidly constructed 

 than has been the case with such instruments, so that there shall 

 be perfect rigidity. 



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