22 DIATOMAGEJL 



one side of it. Running on this rod, and so arranged that they 

 may be fixed by set-screws at any height, are a series of rings 

 of various diameters, which are to be used to hold the vessels 

 in which the specimens are to be manipulated over the source 

 of heat used. Mr. C. G. Bush, late of Boston, Mass., who has 

 had considerable experience in cleaning diatomacese, tells me 

 that he uses a lamp burning petroleum oil, as cheaper than a 

 spirit lamp, and, to support the vessels he employs, has a little 

 metal arrangement on the top of the chimney, such as is sup- 

 plied for the purpose of holding a small tea-kettle and the like. 

 The only objection to the oil lamp is, that, unless the wick be 

 w r ell turned down, we are liable to have our vessels blackened. 

 However, the heat given off by burning petroleum is very 

 great, and I have often used such a lamp with advantage. If 

 desired, of course, the source of heat may be gas, burned in a 

 Bunsen's burner, or a spirit-lamp; and this last, especially if it 

 be supplied with a metal chimney to cut off draughts, is, all 

 things considered, the best, as it is very cleanly, not being 

 liable to smoke the bottom of the glass or porcelain vessels 

 used. If w T e are going to work with large quantities of mate- 

 rial, we shall require a small sand-bath to heat the glass vessels 

 upon. In small quantities, the diatoms may be boiled in test- 

 tubes, when some sort of holder will be required. The metal 

 ones, sold by 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 fore-finger 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 con- 

 ductor of heat; or the paper strip may be grasped in an "Amer- 

 ican clothes-peg," which has a spring to force its parts together. 

 Large quantities of diatoms are best boiled in porcelain evap- 

 orating-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 



