NOTES AND MEMORANDA. 



469 



The ivory points being well oiled, fill the pan with alcohol, so as 

 to cover the top of the specimen ; place the tripod over the pan, 

 and as far to the left as possible ; turn up the screw F until the top 

 of the object to be cut reaches the blade ; push the tripod forward 

 from left to right, and the blade will shave the top of the preparation ; 

 draw the tripod from the glass B for half an inch, or raise the leg of 

 the tripod resting on D half an inch ; it can then be pushed to the 

 end of the glass plates fi'om which it started without the knife touch- 

 ing at any point. Now let the tripod approach the glass B until the 

 points 1 and 2 touch the glass ; turn the screw F so as to elevate the 

 pan more or less, according to the desired thickness of the section ; 

 again repeat the moving of the tripod as already described, and a 

 section is obtained of uniform thickness and any desired thinness the 

 blade is capable of cutting. With a well hardened specimen and a 

 very thin, sharp blade, sections three-fourths of an inch wide, 1 inch 

 long, and l-2100th part of an inch thick can readily be made. Very 

 delicate objects need to be imbedded in wax or paraffin ; ordinary 

 ones are held by the clamp L without any such preparation. 



The whole instrument weighs about 16 lbs., and costs about 

 twenty-five dollars, not including the blades. The cost of four or 

 five blades is not far from five dollars, or one dollar each. 



Electrical Mounting Table.— Mr. F. M. Eogers, of Moorgate 

 Station Buildings, E.G., communicates the following : — Microscopists 

 who mount their own objects must have felt the want of a mounting 

 table that would automatically run at any desired rate of speed, 

 while allowing the mounter free use of both his hando. The instru- 

 ment represented in the woodcuts, which has been devised by him, 

 supplies these requirements, the motive power being electricity, 

 derived preferably from a small and very inexpensive bichromate 

 battery. 



Fig. 6. 



Upon joining up the two connecting wires from the battery to the 

 terminals marked A, Figs. 6 and 7, a current flows through the 

 insulated wire A- surrounding the bar of soft iron B, which is 

 pivoted to the spindle D, and carries the table E. The bar is thus 

 rendered powerfully magnetic, and instantly turns towards the top of 

 the nearest inclined armature, of which there are six, C^ (Fig. 8), cast 



