56 THE MICEOSCOPIST. 



2dly. In some preservative fluid. 



3dly. In Canada balsam. 



The glass slides should be clear, free from veins and bub- 

 bles, of uniform length and breadth, and should have their 

 edges ground smooth by rubbing them on a flat cast-iron plate 

 with emery and water. 



Sections of teeth and bone, and of some kinds of wood, 

 hairs of animals, scales of butterflies, test objects from the 

 infusoria, &c., are best mounted dry ; but all very delicate 

 animal and vegetable tissues, to exhibit their structure clearly, 

 should not be mounted in the dry way, nor in Canada balsam, 

 but in some preservative fluid. 



PRESERVING FLUIDS. A very considerable number have 

 been recommended by different observers. A mixture of salt 

 and water was used by Dr. Cook for this purpose; there is an 

 objection to it, however, owing to the development of a con- 

 fer void vegetable. 



Mr. J. T. Cooper, some years since, made some experiments 

 with a view to determine the best fluid for preserving vegetable 

 colored tissues, such as some of the smaller fungi, and found 

 that salt and water, 5 grains to the ounce of water, to which 

 acetic acid had been added, answered very well. A few drops 

 of creosote or of camphor will prevent the growth of confervas. 



One part alcohol to 5 of distilled water, will preserve even 

 very delicate colors. There is, however, the same objection to 

 the use of this fluid as to the salt and water. When this is used, 

 asphaltum cement may be employed for securing the thin glass 

 cover to the cell. 



Pure glycerine is prepared by the London opticians as a 

 preservative fluid, and is used in the proportion of 1 part to 2 

 of water. Its oily nature, however, often causes much diffi- 

 culty in cementing the thin glass cover upon it. 



A weak solution of chromic acid, one part to twenty of 



