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Stephenson. What he had brought before them was a simple 

 adaptation to an ordinary microscope which only cost a few 

 shillings and therefore was within reach of all. The objection 

 taken by Mr. Michael would be of force if the stage was one 

 of the ordinary kind, but this was so small, and of the horse- 

 shoe form, so that any amount of light could get at the object. 

 He had found it a very great convenience as a special adap- 

 tation to an ordinary microscope. 



Mr. Swift said he made a Stephenson binocular for the late 

 Mr. Tarn, which worked exceedingly well up to Jin. Mr. 

 Stephenson gave him the formula for two sets of prisms, one 

 for high and one for low powers. 



The President moved a vote of thanks to Dr. Tatham for 

 bringing this matter before them. He was glad to hear that 

 the Stephenson form had been made with two sets of prisms, 

 as this would probably greatly improve its performance. His 

 own experience with it had been unfortunately not very satis- 

 factory ; he had seen a good many binoculars, but never one so 

 good as Wenham's. 



Mr. Michael would not like to say that even in the finest 

 instruments the Wenham was not the best, but when the 

 Stephenson form was made as well as the Wenham, the result 

 was far from unsatisfactory. The highest definition was not 

 perhaps to be had with the Stephenson form, but for its 

 working properties it was beyond all comparison the most 

 desirable. 



Mr. Nelson exhibited a Swift's portable microscope, and said 

 that he would not detain the meeting by going over the points 

 in this excellent design, which had been brought to their 

 notice on a former occasion. He would, therefore, confine his 

 remarks to what was novel in the instrument before them. 

 The stage has been increased to a size of 5in. in width and 

 4^in. in depth. This extra depth allows the use of a long 

 guide on the left hand side of the frictional mechanical stage. 

 The body being fitted with three draw-tubes gives a range 

 of adjustment of 8in., namely, from 4|in. to 12 J in. The 

 case is not much increased in size, being Gin. by 5|in. by 7|in. 

 The fine adjustment is on the Campbell differential plan. The 

 threads are cut to foreign gauges, on the metrical system, so 

 that a revolution of the head indicates some integral fraction 



