8 Transactions of the Society. 



carried out without any difficulty by observing the reflected image 

 on the subsidiary screen already described. 



No unusual arrangement for controlling the fine-adjustment of 

 the Microscope at a distance is suggested, as there does not appear 

 to be any reason why any recognized metliod should not be adopted. 

 The arrangement before you is a very simple one, on well-known 

 principles. A central metal rod has a large milled head at the 

 operating end, and a grooved pulley at the other, with a rubber 

 ring stretched on it. This is pushed into contact with another 

 wheel supported on a metal arm underneath the Microscope base- 

 plate, and may be connected by a waxed silk thread, or by any 

 other suitable arrangement with the Microscope. By varying the 

 relavive size of the latter wheels it is obviously easy to alter the fine- 

 adjustment speed, making it faster or slower to suit the require- 

 ments of the user. 



The base-plate designed to carry th.e Microscope is so arranged 

 that almost any type of instrument, whether on a horseshoe or 

 tripod foot, may be used at will. There is a clamp provided which 

 renders it possible for the Microscope to be fastened down, although 

 I venture to su^afest that if the latter is designed as it should be 



CO o 



for photomicrographic work, it should not require to be held at all. 

 However, a clamp is provided and is available for any type of 

 instrttment. 



The position of the Microscope on the base-plate is determined 

 by a slotted right-angled piece of brass, which maybe permanently 

 fixed in the position required. The Microscope is therefore simply 

 put down in position, and there is sufficient range of adjustment 

 to enable it to be centred once and for all. 



All the subsidiary apparatus carried on the geometric slides 

 which move on the swinging tail-piece, are mounted so that they 

 may be centred accurately to the optic axis of the instrument, 

 and may be clamped down when once their position has been 

 determined. 



Tlie apparatus is not in any sense an experimental one, as I 

 have had a similar one in use for many years, M'hich was originally 

 designed by Dr. Carver and myself for the Lister Institute. It has 

 certainly been modified and altered from time to time, and perhaps 

 does not bear much resemblance to wliat it originally was, but the 

 main principles remain the same. The one before you has been 

 made by ]\Iessrs. Charles Baker. I wish to express my apprecia- 

 tion of the assistance and advice that Mr. Lees Curties has so 

 readily given me, without which, I have not the least hesitation 

 in saying, the apparatus before you would never have come into 

 existence. 



