THE PRESIDENT'S ADDRESS. 15 



No. 1 will be invisible if the stand is changed for their 

 portable. Leaving the portable instrument out of the question 

 the image with a large massive stand is always superior to 

 that obtained with a small and lighter stand, however well 

 made it may be, the optical apparatus being the same in both 

 cases. Now the objection to the claw foot is, first, insufficient 

 spread, and secondly, the breadth of the back foot. The first 

 fault makes the instrument easily capsizable sideways, and 

 the second tends to make it rock on four points. The proper 

 remedy for the first fault is to increase the base, and for the 

 second is to make the stand a true tripod. My objection to 

 the cutting and pivoting of the back leg is that it at once 

 degrades the instrument to the level of a portable stand ; but 

 if the instrument is put forward as a new portable microscope 

 it will probably be admitted that it is about the best form that 

 has yet been devised. 



There is another innovation with regard to this stand, and the 

 former pattern brought forward by Messrs. Swift and Son, 

 which suggests an important question for the consideration of 

 microscopists, viz. : is it an advantage to make the legs of the 

 tripod or tetrapod hollow ? Lightness is of course gained, but 

 then it is at the cost of a higher centre of gravity, and more- 

 over how about rigidity ? If these stands are intended for 

 portable microscopes only, the lighter the better, and on that 

 account one is prepared to sacrifice something. If on the other 

 hand they are intended for the highest possible work, solid legs 

 would perhaps be better ; probably by filling up the tubes 

 with lead the necessary weight and rigidity would be secured. 



With regard to the next two instruments, you will know 

 more about them than I, for they were exhibited here during 

 my absence, so unfortunately I have not seen them ; they 

 are dirties' instantaneous photomicrographic shutter, and 

 Leitz's low-power projection camera. 



We now come to a great, and what we may venture to 

 think will prove a most useful invention, viz., Swift's 

 friction geared mechanical stage.* It has since its first in- 



* Frictional gearing was first applied to the microscope by F. H. Wenham, 

 who says that " he found it answer perfectly well in lieu of the ordinary 

 rack-and-pinion of the body and stage of microscopes .... it works very 

 smoothly and lifts a weight of 161bs. without slipping." — "Quart. Journ. 

 Micro. Science," Vol. vii., p. 201, two woodcuts (1859). 



