OE MICROSCOPIC OBJECTS. 69 



<copic objects, but as instructive specimens. It is not, 

 -therefore, sufficient to take a single slide as all that is 

 required, but to have the same diatom prepared in as many 

 ways as possible. The following are the principal : 



1. Mounted crude in fluid (see Chapter V.) 



2. Burnt crude upon the cover, and mounted dry or in 



balsam. 



3. Mounted dry or in balsam (see Chapter IV.), after 



the cleansing process already described. 



I will here give Mr. Rjlands' method of mounting them 

 dry, the fluid and balsam preparations being noticed in 

 their respective chapters. The slide, with the ring of 

 asphalt, or black varnish, should have been prepared some 

 weeks previously, in order to allow it to dry thoroughly. 

 When required, it must be held over the spirit-lamp or 

 Bunsen's burner until the ring of varnish is softened. The 

 burnt cover, having been heated at the same time, must 

 then be taken in the forceps and pressed upon the softened 

 tarnish until it adhere all round. When cold, an outer 

 ring of asphalt completes the slide. 



Such is the method which my friend Mr. T. G. Bylands 

 employs in the preparation of diatoms for the microscope. 

 I have said enough concerning his results. It is to be 

 feared, however, that to some these several modes of opera- 

 tion may appear lengthy and complicated ; but if read 

 carefully, and the experiments tried, they will be found to 

 be simple enough in practice, and to occupy much less time 

 than an intelligible 'description would lead the novice to 

 Relieve necessary, 



The minute nature of diatom forms, and the high micros- 

 copic powers by which they are examined, render a very 

 shallow cell necessary when they are mounted upon a dry 

 slide. Many early attempts, on this account, have been 

 ruined by the cement used to fix the thin cover spreading 

 nnderneath. A correspondent of the " Monthly Microscopic 

 Journal " thus gives his mode of avoiding this : " There is 

 a. very simple means of avoiding this danger, and I will 



