1884.] 



MICROSCOPICAL JOURNAL. 



29 



square off. Smooth both ends by 

 heating them in the flame, while con- 

 stantly turning the tube on its axis. 



It is an excellent plan to have con- 

 stantly on the table with the micros- 

 cope a wide-mouth bottle of 3-4 ounces 

 capacity filled with clean water in 

 which the tubes and rods in use are 

 placed. Such a bottle of tubes should 

 be always at hand, w^hile making ob- 

 servations, as it ensures clean tubes 

 and fresh w^ater, which are in constant 

 demand. 



Medicine droppers are very con- 

 venient for applying reagents drop by 

 drop. They may be inserted through 

 the corks of reagent bottles, and thus 

 be ready for instant use. A solid glass 

 rod, however, running through the 

 cork w^ill serve every purpose. ' 



For cleaning cover-glasses it isw^ell 

 to have a couple of large flat corks cov- 

 ered with chamois skin on one side. By 

 placing the cover-glass between them 

 and rubbing, it is well cleaned and 

 polished. Many persons, hov^^ever, 

 clean their cover-glasses with a bit of 

 soft cloth, and after a very little prac- 

 tice not many need be broken in this 

 way. 



In mounting objects it will be fre- 

 quently necessary to hold the cover- 

 glasses down firmly. This is often 

 done by the aid of brass clips made 

 for the purpose, but a more conven- 

 ient method is to use heavy rifle bul- 

 lets, which can be set upon the cover 

 and left until the cement is quite stiff 

 and hard. The bullets should be 

 heavy, weighing fully an ounce. 



For mounting objects of consider- 

 able thickness rings w^ith an external 

 diameter slightly greater than the 

 cover-glasses must be used. Rings of 

 gutta-percha, paper, block-tin, and of 

 almost every imaginable substance 

 have been used, but as it is not intended 

 to exhaust the subject in the articles, 

 but to indicate what is good and read- 

 ily obtained by any person, we only 

 recommend the common brass cur- 

 tain-rings, vs^hich can be obtained suit- 

 able for 1^ and |^ covers at the hard- 

 ware shops for a few^ cents per dozen . 



A good turn-table is essental if neat 

 mounts are to be made. A self-cen- 

 tering one saves time and is a great 

 convenience, but many ot the best 

 mounters do not use them. There 

 are so many forms of turn-tables in 

 the market that it is hard to say what 

 are the most desirable ones. Bul- 

 loch's "volute" turn-table is a most 

 excellent one. A good form w^as in- 

 troduced some time ago by Messrs. 

 Bausch and Lomb,* and Mr. Zent- 

 mayer has just perfected a new one, 

 which is described in these columns 

 this month. 



Passing now to a consideration of 

 cements, varnishes, etc., only those 

 will be mentioned that are known to 

 be durable. The number of cements 

 used by different persons in mounting 

 is surprising, considering that a very 

 fev^^ of them serve for all purposes, 

 and have been proved durable by long 

 use. If the reader desires to make a 

 series of comparative experiments on 

 cements, that is one thing, but if he 

 desires to mount objects for perma- 

 nent use he had better leave such ex- 

 perimenting to others. No definite 

 results can be obtained concerning the 

 value of a cement in less than three 

 or four years' time , and even this period 

 is not sufficient for positive conclu- 

 sions. It is therefore better to use 

 cements that are knoAvn to be satis- 

 factory, and in this article we pro- 

 pose to mention only such as we know 

 to be reliable. 



At the head of the list, as being 

 more universally useful than any other, 

 w^e would place shellac dissolved in 

 alcohol. The simple alcoholic solu- 

 tion of brown shellac, with a few drops 

 of castor oil to make it flow better, is 

 what we have used most frequently. 

 There are various mixtures sold, hovv^- 

 ever, in which shellac is the basis that 

 are said to be superior to the simple 

 solution. Among these the best known 

 are Bell's cement, and Ward's brown 

 cement. The great fault of shellac is 

 its brittleness. This, however, is of 



* Vol. ii, p. 226. 



