38 



NAME TO EE WRITTEN ON THE SLIDE. 



necessity of applying another drop, thereby involving 

 the risk of air-bubbles. This operation having been 

 satisfactorily achieved, the thin glass cover is to be laid 

 on, placing it on the apex of the drop ; and then on the 

 cover lay a piece of stout sheet-lead, of nearly the same 

 dimensions, which will gradually press out the balsam 

 between the glasses. These are now to be laid aside, 

 in a horizontal position, for a week, when the lead 

 weight may be removed. The name may then be writ- 

 ten on the glass ; and it is not advisable to place the 

 slide vertically, or to trim the edges, for the space of a 

 month, as the balsam dries very slowly. 



This plan is recommended to those who may be de- 

 sirous to investigate marine Algse microscopically. 



It is, indeed, at all times very desirable to possess even 

 but a fragment of a duly-authenticated specimen, with 

 which to compare one of our own collection. The col- 

 lector will find no more certain plan for effectual com- 

 parison, than to take a glass slide, with its mounted 

 specimen, and place beside it a fragment of the plant 

 under inspection, and examine both at the same time, 

 with a good single magnifier. 



Comparing recent with dried specimens will not often 

 be very satisfactory, because many plants alter much in 

 their appearance in drying ; whereas the mounted spe- 

 cimen, if properly prepared, will generally preserve its 

 natural form and similitude ; and then, on comparing 



