324 H. MORLAND ON MOUNTING DIATOMACEJ5. 



smaller of these pieces of brass I place my cover-glass with my 

 arranged diatoms and pick the same np again with a drop 

 of balsam or styrax placed on the centre of a slip, said slip 

 being turned over the prepared cover-glass and centred, centre 

 to centre ; one end of the slip resting on the larger of the pieces 

 of brass, which is simply for the purpose of steadying the slip 

 and keeping it fairly square and level with the cover on the 

 smaller piece. It will be noted that the larger piece is slightly 

 thicker than the smaller, which is to allow for the additional 

 thickness of the cover-glass. Thirdly and lastly, I have a 

 3" X I* glass slip, with one of the angles cut off and the small 

 end rounded off at a grindstone, thus : — / 



This slip is only for use when one has to 



deal with material containing a quantity of very fine sand. By 

 placing two or three drops of water containing such material on 

 the centre of this slip and then tilting the whole off again 

 rapidly past the pointed end on to an ordinary slip or cover, the 

 bulk of the sand, with very few diatoms, will be left behind on 

 the pointed slip. A very few trials will enable anyone to 

 acquire the knack required. 



I have two methods of preparing slides of " selected '' 

 diatoms, one where the diatoms are in no way fixed with gum or 

 other cement, the other where I use gum for this purpose. 



Proceeding to describe my first method, I may say that this 

 plan will only answer for the finer and flatter diatoms, and 

 success is more certain if styrax be used instead of balsam. It 

 is, to say the least, a very risky plan, as the diatoms are very 

 apt to get displaced even after the slides have been finished off 

 for some time, but, on the other hand, the requisite knack is 

 easily acquired, and when the mount is successful the result is 

 simply perfection ; such a mount can fearlessly be placed under 

 the very 'highest powers. 



To begin, I first allow a drop of water containing my material 

 to evaporate on an ordinary 3" x 1" slip, taking care that the 

 diatoms are not too crowded together ; from the dried material 

 I select my diatoms under the microscope by means of one of 

 my " mounting bristles ; ' these I place just outside the outer 

 edge of the dried material for use as required, as I make it a 

 rule never to select my diatoms on the days that I mount them, 

 though occasionally this rule is broken. Having a number of 



