PRESERVATION OF ALGJ3. 93 



way : to sixteen parts of distilled water add one part of rectified spirits 

 of wine, and a few drops of creosote, sufficient to saturate it ; stir in a 

 small quantity of prepared chalk, and then filter ; with this fluid mix 

 an equal measure of camphor- water (water saturated with camphor) ; 

 and before using strain off through a piece of fine linen. 



This fluid I do not find to alter the appearance of the endochrome 

 of algse more than distilled water alone does after some time ; and there 

 is certainly less probability of confervoid filaments making their ap- 

 pearance in the preparations ; and there would seem to be nothing to 

 prevent such a growth from taking place, when the object is mounted 

 in water only, provided a germ of one of these minute plants happen 

 to be present, as well as a small quantity of free carbonic acid. 



Fluids containing a larger quantity of spirits of wine, and conse- 

 quently of creosote also, than the one of which I have given the for- 

 mula, produce a greater change in the appearance of the endochrome. 



My method of making cells in which to mount preparations of 

 algae is as follows : some objects require very shallow, and others 

 somewhat deeper cells. The former may be made with a mixture of ja- 

 panners' gold size and litharge, to which (if a dark colour is preferred) 

 a small quantity of lamp-black can be added. These materials should 

 be rubbed up together with a painter's muller, and the mixture laid 

 on the slips of glass with a camel-hair pencil as expeditiously as pos- 

 sible, since it quickly becomes hard ; so that it is expedient to make 

 but a small quantity at a time. For the deeper cells marine-glue 

 answers extremely well, provided it is not too soft. It must be 

 melted and dropped upon the slip of glass ; then flattened, whilst 

 warm, with a piece of wet glass, and what is superfluous cut away 

 with a knife, so as to leave only the walls of the cell ; these, if they 

 have become loosened, may be made firm again by warming the under 

 surface of the slip of glass. The surface of the cells must be made 

 quite flat j which can be easily done by rubbing them upon a wet 

 piece of smooth marble, covered with the finest emery-powder. 



When about to mount a preparation, a very thin layer of gold- 

 size must be put upon the wall of the cell, as well as on the edge 

 of the piece of thin glass which is to cover it ; before this is quite dry, 

 the fluid with the object is to be put into the cell, and the cover of 

 thin glass slowly laid upon it, beginning at one end ; gentle pressure 

 must then be used to squeeze out the superfluous fluid j and, after care- 

 fully wiping the slide dry, a thin coat of gold-size should be applied 

 round the edge of the cell, and a second coat so soon as the first is 

 dry ; a thin coat or two of black sealing-wax varnish may then be put 



