756 Transactions of the Society. 



On page 432, Fig. 84, is shown a so-called improvement, though 

 one which is useless, inasmuch as the razor is incapable of being 

 levelled, and therefore cannot be kept parallel with the slides on 

 which it works, the result being that no sections with parallel 

 surfaces, and therefore no thin sections, can be cut. 



The present further modification, Fig. 146, has consequently 

 been made by Mr. Swift, of Tottenham Court Road, at my request. 

 The machine now resembles that last mentioned in having an iron 

 bracket with spring tube to receive either of the four holders for 

 material, Figs. 84-7, and a clamp below by which it may be fixed 

 to a table ; but differs from it in that it has the glass top and razor- 

 frame of the original Williams microtome. 



The new Microtome, therefore, consists of an iron bracket to the 

 top of which is fixed a glass plate with central aperture. Through 

 this passes the upper end of the apparatus for holding the material 

 to be cut, either for freezing by ether as in Figs. 146 and 84, or 

 by ice and salt, as in that known as Pritchard's, Fig. 85, or for 

 material imbedded, Fig. 86, or for clamping a tree stem or other 

 structure not requiring to be frozen or imbedded. Each of these 

 is held below the top in a spring tube capable of being tightened by 

 a screw, and the whole instrument can be fixed to a table by a 

 clamp which forms the bottom of the bracket. The sections are 

 cut by a razor held in a Williams triangular frame, which is 

 levelled by means of two base screws, and lowered for each section 

 by means of the apex screw. 



When using the ether freezing apparatus with this microtome, 

 material to the thickness of ^ inch can be frozen in H minutes, 

 and good successive sections cut as thin as can be obtained by any 

 microtome. When the material is once frozen scarcely any 

 ether is required to keep up the action, so that the cost of the 

 ether is rather less than that of ice, methylated ether sp. gr. *720 

 at Is. Gd. a lb. being used. 



