Examination and Study hy means of the Microscope. 229 



dealers in chemists' apparatus, are extremely handy; but I have 

 found that we can make very good ones out of old paper collars. 

 One of the kind called " cloth-lined " may be cut into strips about 

 three-quarters of an inch wide and three inches long. Such a strip 

 is folded around the test-tube near the top, and the ends, brought 

 together, are held between the forefinger and thumb. In this way 

 the tube is firmly grasped, and can be held over the lamp without 

 much danger of burning the hand, as the paper collar strip is a 

 bad conductor of heat ; or the paper strip may be grasped in an 

 " American clothes-peg," which has a spring to force its parts 

 together. Large quantities of diatoms are best boiled in porcelain 

 evaporating dishes, glass flasks, or beaker glasses. The last-men- 

 tioned vessels are also by far the best things for washing them in. 

 A few, say three or four, glass stirring-rods will be found useful ; and 

 one or two American clothes-pegs to take hold of hot evaporating 

 dishes with. Then there will be required a few dip-tubes, made of 

 small glass tube, drawn out over a flame, so that the opening is con- 

 siderably diminished. The mode of making these cannot be given 

 here, but will be foimd in books on chemical manipulation ; and it 

 will be well for the student to learn to make his own dip-tubes, as a 

 number will be required first and last, and they are easily broken. 

 Of course there will be required a number of glass slides of the 

 usual dimensions of three inches by one. These should be of as 

 white glass as possible, and it will be found best to procure those 

 with ground edges, as they are the neatest in appearance. Only such 

 as are free from scratches or other blemishes in the central square 

 inch should be used ; and although even such as have bubbles or 

 scratches near the ends only will not look ornamental in a cabinet, 

 we should remember that microscopic objects are not generally 

 mounted to look well in a cabinet, but to be useful out of it ; so that 

 if the central and useful portion of the slide be perfect it need not 

 be rejected. Some persons make their own glass slides, but I have 

 never found it answer to do so, as it is difficult to get the right 

 kind of glass, not at all easy to cut it or grind the edges, and it is 

 Hable to be scratched while cutting or grinding. Thin glass, such 

 as is made on purpose for microscopic use, will be required ; and 

 this, also, it will be found best to buy ready cut than attempt to cut 

 it for one's self. The thin glass used for covers may be of different 

 thicknesses, but the thickest made will not do for diatoms, and a 

 certain a,mount of the very thinnest will be required for small and 

 delicately marked forms, on which very high power objectives will 

 have to be used. The covers must be perfectly clean, which may 

 be ensured by soaking in caustic potassa solution, and then washing 

 thoroughly in clean water. The thinner kinds of glass are rather 

 difficult to clean ; but with a httle extra caution it may be accom- 

 plished, the last polish being given to it by a piece of an old and 



