8 PROCEEDINGS OF THE ACADEMY OF 



But structures such as recent teeth and bone, the hardened albumen of 

 kernels of such nuts as that of Phytclcphas macrocarpa, brain, sand, &c., bear 

 heat indifferently. They crack, but more provokingly warp, when attempts 

 are made to fix a first surface. Indeed, when not properly dried after the 

 performance of the first step of the process already described, they usually 

 warp so much as to render the making of a uniformly thin section impossible. 

 To remedy the defect of the heat process I found a matter of much difficulty ; 

 so I employed a new one, which I claim to be easy, certain and original. 



To make sections by the method I have so successfully employed but little 

 apparatus is required. A couple of Arkansas hones, the one coarser, the other 

 very fine, and both kept^^o^ by rubbing upon a hard marble flag with flour of 

 emery and water, are of first necessity. I also recommend that the hones 

 while being "faced" should be pushed steadily along diagonally, first ono 

 way and then the other, so that the surface will be "set" or finished quin- 

 cuntially. 



In the next place I mention fine Russian isinglass for glue, to be boiled, 

 strained, and dried in flakes upon a polished metal surface. Then thin letter 

 paper is to be jirovided ; several bits of thick mirror glass, for holders, ground 

 on the edges, of different sizes, from one inch square upwards, according to 

 the size of the projected section, as also sweet oil and a little chloroform. And 

 finally there will be needed some alcohol, and a small quantity of eleutriated 

 polishing putty, oxyd of tin, as used by stoue cutters. 



As a preliminary it is desirable that some definite idea as to the plane of 

 the section be entertained, and this is possible for all except minute frag- 

 ments. Then the saw cuts out a small block, say of one-eighth inch in thick- 

 ness, or the file reduces a mass to near the desired level. Now the object is 

 moved steadily and rather lightly along over the coarser hone, wet with wa- 

 ter, and then over the finer one, the operator being careful to pass the object 

 evenly beckwards and forwards, to turn it about from tim^ to time, and to 

 examine the surface frequently with a lens to detect invidious scratches. 

 Teeth and similar objects should be pushed along in one direction only, the 

 enamel forward in the case of teeth, so as to avoid and prevent separation of 

 their different constituents. 



When a perfect surface shall have been obtained let the specimen be 

 washed in water and then immediately dropped into alcohol, which, ab- 

 stracting water from every part alike, dries the object — so far as aqueous wet- 

 ting is concerned — and no warping occurs. Next, strain a bit of chamois 

 skin upon a block, sprinkle upon it a little of the polishing powder, moisten 

 all with alcohol, and polish tbe first surface by rubbing it with gentle force 

 upon the prepared skin. After receiving polish the specimen is to be restored 

 to its alcoholic bath. 



The succeeding step of the operation consists in melting a little of the isin- 

 glass in a silver spoon or other more convenient metallic receptacle, making 

 a fluid of the consistence of cream, and adding, at the end, a few drops of 

 alcohol to increase the tenacity by making the thin glue take better to the 

 polished surface. Warm one of the glass bidders very slightly, with the fin- 

 ger varnish one of its faces over with the glue, prepare a bit of the thin paper 

 in like manner, and quickly cement the paper evenly upon the glass. Trim 

 awaj' the edges with scissors and the paper is ready for the guides^ which 

 are two little ribbons of paper about a quarter of an inch wide, and to be 

 glued on the paper-facing on opposite sides and touching the margins. The 

 thickness of the guides determines the thickness of the future section, for be- 

 tween them is left a gutter in which this section will lie. Now with the fin- 

 ger place a film of glue upon the paper between the guides; and, having pre- 

 viously wiped the object quickly dry, slightly moisten its surface and edges 

 with the isinglass, apply the s[)ecimen dexterously, make forcible pressure, 

 and confine it by wrapping it tightly with strong thread. -It is to be observed 

 that the isinglass should not exceed the area limited by the guides, nor should 



