322 H. MORLAND ON MOUNTING DIATOMACE.E. 



up defects in the way of dirt, or else the fixing cement by which 

 the diatoms are attached to the cover-glass becomes distinctly 

 apparent. However, as, on the other hand, my efforts are often 

 crowned with success, I venture to now describe the plans which 

 I adopt. 



First and foremost as a very material aid to success it is 

 absolutely necessary to select and mount the diatoms under a 

 fairly good magnification, as otherwise one can only guess at 

 what he is doing, whereas absolute knowledge is required. The 

 power I employ is one of 60 diameters. I use a Stephenson's 

 binocular, which has the advantage not only of erecting the 

 image, but also of a large horizontal stage. To the tube of this 

 microscope I attach in front a piece of jin. glass tubing, about 

 four inches long, so arranged and bent that the lower end points 

 immediately under the objective I am using, but not projecting 

 far enough to be seen when I look through the microscope. On 

 the other end of this tube I fix a piece of india-rubber tubing, 

 with a glass mouthpiece, which I bring over the front of my 

 microscope betw r een the eye-pieces and allow to hang down be- 

 hind ; this is my " breathing- tube," the use of which I will 

 explain later on. This breathing tube being fixed to the tube 

 of the microscope works up and down with it w 7 hen the latter 

 is being focused, and always has the same relative position with 

 the objective after it is once fixed in its place, but can be turned 

 away on one side if desired. Should this tube at any time get 

 very w r et internally through being used, it can soon be dried 

 again by simply drawing the breath through it for a short time. 



My mounted bristles take next rank ; of these I have some 

 seven or eight always b}^ me of various degrees of fineness and 

 in duplicate for fear of accidents whilst mounting. It is very 

 important to have good bristles, and I was a long time before I 

 could get exactly what I wanted ; the attributes of a good bristle 

 are that it should be fairly stiff and taper suddenly to a very fine 

 point. 1 obtain mine from a certain clothes brush which I 

 have at home, examining it carefully under a Coddington and 

 selecting those bristles which meet my requirements. I then 

 mount them in slender handles in a cleft (so that they can be 

 placed centrally) and afterwards whip round with tln'ead, 

 varnishing the same over with liquid marine glue. I have heard 

 a good deal about split bristles from shaving-brushes, but could 



