COLLECTION, EXAMINATION, ETC. 321 



bottle is impracticable these fragments of pumice 

 may be got rid of by covering the section with a 

 little of the balsam solution and heating it, when the 

 ebullition of the medium will bring the particles to 

 the surface with the air-bubbles, when they may be 

 removed, as they form, with a fine brush. 



' Careful observance of these directions will 

 ensure success, after perhaps a failure or two ; 

 the most annoying casualty being that often, at the 

 last moment, a too vigorous rub may wipe the whole 

 section out of existence, in which case the only 

 thing you can do is to begin again upon another 

 specimen.' 



The above excellent description is given in full, 

 since, if these minute instructions are carefully 

 followed, there is more chance of success. 



The following method for hardening and slicing 

 friable deposits and loose sands has been devised by 

 ¥. G. Pearcey, and used with much success in the 

 ' Challenger ' Ofiice :— 



The dried deposit or sand is placed in a small 

 pill box, upon which is poured a solution of mastic 

 dissolved in benzole. The mass is hardened by 

 slowly heating in a hot-water oven, and when cold 

 the piece is sliced into layers about y^^ inch thick or 

 more. These slices are rubbed down and polished 

 upon the snakestone, after being cemented to a 

 thin glass, which in turn is fastened to a glass slip. 

 When one surface has been sufficiently prepared, the 

 cover glass is removed by a gentle warming, and 

 then cemented in the reverse position with Canada 



Y 



