' MAKING SECTIONS Or WOOD, ETC. 341 



the thin glass cell, page 291, or in that shown at fig. 176, 

 page 285, and in the manner described at page 284. If the 

 sections be dark, they may be mounted in Canada balsam in 

 the manner described at page 306 ; but if they become too 

 transparent when immersed in it, they should be first charred 

 by being placed between two plates of glass, and subjected to 

 the heat of an argand lamp until they turn brown, or they 

 may be dyed with tincture of iodine, or in a decoction of 

 fustic or logwood. Transverse sections may be moimted in 

 this way, as they will stand the process of charring very well, 

 but all the other kinds, especially those that exhibit large 

 spiral vessels and dotted ducts, are best mounted in fluid. If 

 the sections are to be mounted dry, they may be prepared in 

 the manner before described at page 313, or they may be 

 placed between two glasses, with bevelled edges, that are 

 filled up with sealing-wax after the plan of Mr. Darker, before 

 described in page 317 ; in all these cases, particular attention 

 should be paid, so that the sections be properly dried before 

 they are placed between the glasses, otherwise fungi are apt 

 to grow from them. 



Chippijigs of Wood. — An excellent method of exhibiting the 

 medullary rays, and some of the larger vessels of the harder 

 woods, is by making small chippings of them, or by tearing 

 short pieces of wood in halves lengthways of the grain, 

 after the beginning of a split has been made by a chisel or a 

 knife; these should be mounted on discs as opaque objects, 

 and examined with a magnifying power from one hundred to 

 two hundred diameters, the Lieberkuhn being employed as 

 the illuminator. 



Sections of Horns, Hairs, Sfc. — These may be made with the 

 cutting-machine in the same manner as those of wood ; all the 

 very tough kinds, such as the horn of the rhinoceros, will be 

 easily cut after having been boiled for a short time in water ; 

 they should be placed in the machine and cut whilst warm, 

 otherwise the boiling will have no beneficial efiect. If the 

 specimens be too small to be cut to fit the hole in the cutting- 

 machine, they may be firmly wedged up by pieces of wood. 

 For the purpose of making sections of the porcupine's quill, 



