8 



HARDIVICKE'S SCIENCE-GOSSIP. 



a small piece out of the circumference of the india- 

 rubber ring, and place it on the slide between the 

 sheaths, with the opening towards one of the long 

 sides of the slide. Place on top of the ring the short 

 piece of glass, and slide the sheaths towards each 

 other, till the small screws project over its ends. 

 Then, by turning down the screws, the ring is com- 

 pressed between the two pieces of glass, and a perfectly 

 water-tight cell results. By using rings of different 

 thickness, cells of eveiy convenient depth may be 

 obtained. 



When one has finished working with it, the whole 



It consists of a block of well-seasoned wood, 

 5X3x3 inches. At \\ inch from one end of the 

 block a hole is bored of such diameter as may be 

 necessary to admit the cylinder of a pewter syringe 

 of about \ inch internal diameter. This hole runs 

 vertically from the upper to the lower surface of the 

 block. Across the opposite end of the block is cut 

 a horizontal notch, \\ inch deep and wide. Cut off 

 the nozzle end of the syringe, so as to leave a piece 

 of tube three inches long, and cut the handle off the 

 plunger so as to leave only the piston part. This 

 should be packed as neatly as possible, and have 



W/Wa 



Fig. 2. — Live Cell. 



" 



^j 



i&. 



Fig. 3. — Elevation of Live Cell. 



1 



Lrl 



_ _" '","" 



z 



% 



§1 



tabl; 



3 



l§3 



Fig. 4. — Inexpensive Microtome. Vert, section. 



thing can be taken to pieces in an instant and 

 cleaned. If a well-polished piece of glass, free from 

 flaws, be chosen for the upper plate, its thickness 

 will not be found to interfere very materially with the 

 performance of any power below J-inch. 



While on the subject of cheap apparatus, I will 

 describe a form of microtome which can be made by 

 any one, with a slight mechanical turn, for about 

 eighteen-pence. In many essential points it is almost 

 identical with that of Mr. A. B. Chapman, described 

 in your June number, as, however, I constructed and 

 used it more than ten years ago, I must claim to be 

 guiltless of plagiarism. 



Fig. 5. — Upper Surface of Microtome. 



soldered to its upper surface a small 

 Z-shaped piece of tin, so as to give the 

 parapin a firm hold on the piston. 



Cement the tube into the hole in the 

 block with shellac or 'elastic glue, so that 

 one end projects about the thickness of a 

 glass slide above the upper surface, and 

 cement on to the upper surface of the block, 

 along each side of the projecting portion 



7 of the syringe, an ordinary ground-edged 



^> glass slide, taking care to choose a pair of 

 equal thickness, and with well-rounded 

 edges. Now procure a fine screw running 



on an oblong-nut : the nut to have a hole 



to take the head of a wood-screw at each 

 end, and secure it by means of a couple of 

 screws to the under surface of the block, so 

 that the fine screw works up and down in 

 the centre of the pewter tube. Get also 

 one of the coarse iron screws with brass 

 fittings, such as are used to fasten old- 

 fashioned window sashes, procurable from 

 any ironmonger, and fasten this to the under 

 surface of block, so that the coarse screw may work 

 into the notch already described. 



To use the machine, place it with the edge of a 

 lath projecting into the horizontal notch. Then by 

 screwing up the coarse screw, it will be firmly 

 clamped to the table, and projecting beyond it, a 

 position extremity convenient for working. 



Now turn down the fine screw, and push the 

 piston, with the finger, down through the tube on 

 to it. The well is then filled with a melted mixture 

 of five parts solid paraffin to one part tallow, 

 and the object to be cut embedded in this. The 

 sections are then taken in the usual way, the two 



