OF MICROSCOPIC OBJECTS. 5 7 



CHAPTER III. 



MOUNTING IN CANADA BALSAM. 



THE nature and use of tliis substance has been before spoken, of, 

 so the method of working with it may be at once described. 



Perfect dryness of the objects is, if possible, more necessary in 

 this mode of mounting than any other, as dampness remaining in 

 the object will assuredly cause a cloudiness to make its appear- 

 ance in a short time after it is fixed. Where pressure does not 

 injure the specimens, they are most successfully treated when first 

 dried betwixt the leaves of a book, or in any other way which may 

 prove most convenient, as noticed in Chapter II. 



Before describing the methods of proceeding with any particu- 

 lar objects, general rules may be given which should be observed 

 in order to succeed in this branch of mounting, 



As the object is to be thoroughly immersed in the balsam, it is 

 evident that when it has once been covered, so it must remain, 

 unless we again free it by a process hereafter mentioned, which is 

 very troublesome ; and on this account there must be nothing 

 whatever in the balsam except the object. The inexperienced 

 may think this an unnecessary caution ; but the greatest difficulty 

 he will meet with is to get rid of minute bubbles of air, perhaps 

 invisible to the naked eye, which appear like small globules when 

 under the microscope, and render the slide unsightly, or even 

 worthless. Ten objects out of eleven contain air, or at least are 

 full of minute holes which are necessarily filled with it ; so that 

 if they should be immersed in any liquid of thick consistency, 

 these cells of air would be imprisoned, and become bubbles. The 

 air, then, must be got rid of, and this is usually accomplished by 

 soaking for some time in turpentine, the period required differing 

 according to the nature of the object. In some cases, the turpen- 

 tine acts upon the colour, or even removes it altogether, so that it 



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