PREPARATION OF DIATOMS. 73 



previously got rid of all alcohol by washings. I prefer to allow the 

 diatom iferous liquid to dry slowly without burning which has always 

 lurnished me with preparations containing some diatoms united in 

 groups and in bands. 



" Nor have I been more successful when I have put the balsam 

 immediately on the diatoms, more particularly when I have been pre- 

 paring large and convex forms such as the Coscinodiscus or Aulacodiscus ; 

 the balsam does not penetrate into the interior. In these cases I 

 previously put a drop of oil of turpentine on the diatoms and when 

 this has thoroughly penetrated the valves I add the balsam and let 

 the whole rest in order that the balsam may slowly take the place of 

 the oil, which is volatile. 



" I have found this necessary sometimes even when using styrax, although 

 this is more fluid than Canada Balsam. 



" Mounting diatoms dry is the easiest process of all, but to prevent 

 as far as possible the diatoms spoiling, which often happens after a short 

 interval, in the first place ihe diatoms must be perfectly washed in distilled 

 water, then the black varnish used for making the cell should not contain 

 any oily matter, as is often the case, and this varnish should be thoroughly 

 dry before applying the cover-glass, which is made to adhere by heating 

 the glass-slip. The black varnish may be advantageously replaced by hard 

 Canada Balsam dissolved in benzine ( I )." 



Mr. / Kinker 1 s Method. My friend, Mr. J. Kinker, is the skilful and 

 learned diatomist, of Amsterdam, who has produced many very remarkable 

 type-slides made after Moller's method. He has shown me in his own 

 laboratory the method which he employs for cleaning diatoms, and we 

 can testify to the advantage of his mode of operation from personal 

 experience. 



He begins by getting rid of the sand by successive washings, and 

 of the lime by treating for a day in hydrochloric acid. Then 

 he washes thoroughly and boils the deposit for fifteen minutes in 

 sulphuric acid, to which has been added a few drops of nitric acid, 

 the fifteen minutes being reckoned from the moment Mr. Kinker lights 

 the gas. 



The boiling is effected in a small glass flask or retort, fitted with 

 a glass stopper, terminating in a long curved tube, which is plunged 

 into an alkaline solution to absorb the acid vapours. The flask is 

 placed in a sand bath. 



1 ) See our previous footnote on gum-lac varnish, p. 70. H. V.H. 



