332 



such as the mole, mouse, weasel, &c, -where it is desired to examine the 

 teeth in situ, and to study them in connection with their alveolar sockets. 

 Sections of rocks can only be cut with a lapidary's wheel, and I have had 

 no experience with that apparatus. Sectons of coal I have tried, but the 

 process is so dirty, that I think it is better to buy them ready made than 

 get begrimed in making them for myself ; I have tried the process of 

 letting the coal soak in a saturated solution of corbonate of potash, but 

 have not succeeded in getting it soft enough to cut with a razor. Very 

 good sections of wood maybe obtained from any cabinet-maker's workshop, 

 from the planings of various woods used by him in his work, selected 

 pieces of the shavings mounted in balsam, make very instructive objects, 

 and many of them will polarise very beautifully." 



Mr. White then proceeded to demonstrate practically his method of grind- 

 ing down a section of tooth, first on a cornndum wheel, and afterwards with 

 ground glass slabs of varying degrees of fineness. He then called upon 

 Mr. Ady, who explained what he termed " the laccic " method of occlusion, 

 substantially as follows : — 



1st. Saw a piece off the tooth or bone, rub it flat on an engineer's file, 

 polish the fiat surface on a fine hone, water of Ayr stone being pre- 

 ferable. 



2nd. Fasten the section on to a piece of plate glass, one inch square, 

 with a cement made by melting six parts of " button " lac with one part 

 Venice turpentine. 



3rd. File the section down moderately thin, and then reduce further on 

 the water of Ayr stone, examining from time to time with the micro- 

 scope. 



4th. Soak the section off with strong methylated spirit, wash thoroughly 

 in clean spirit, and dry between tissue paper. 



5th. Make a thin solution of white shellac in methylated spirit, filter 

 and keep in a stoppered bottle. 



The section is to be dipped in this solution, drained and laid down on 

 a cold plate under a bell glass in about half an hour it will be dry. 



6th. Mount in cold balsam and benzol in preference, in order to avoid 

 heating the section, as that would give it a tendency to curl ; but as the 

 melting point of the shellac is higher than that of balsam, the latter may 

 bo used if thought desirable, as it may even be caused to boil without 

 affecting the shellac. 



After some remarks from Dr. Matthews, Mr. Hardy, and other members, 

 the President closed the discussion by moving a vote of thanks to Mr. White 

 and to Mr. Ady, which was carried unanimously. 



The following objects were exhibited in the Library : — 



Coralline, Clava sqnamata Mr. F. W. Andrew. 



Section of Ovary of Begonia Mr. H. E. Freeman. 



An Alga, mounted in 1864, in glycerine jelly... Mr. H. G. Glasspoole. 



Dendrosoma radians, &c. Mr. J. D. Hardy. 



Diatoms from Tarland, Aberdeenshire Mr. H. Morland. 



Aquatic larva Mr. F. A. Parsons. 



