ZOOLOGY AND EOTA^^:, MICROSCOPY, ETC. 837 



diaphragm, covering its side next the interior of the vessel and passing 

 over the edges, thence upwards, downwards, and laterally through the 

 slit in the vessel and around the outside of the same, as in the former 

 case, rubber bands being applied as before over the upper and under 

 edges of the muslin. There is no particular advantage to be gained 

 by this mode of construction, but it is suggested as a modification 

 which may be deemed desirable by some. 



It is necessary that the holes in the vessel be bored at some dis- 

 tance from the top of the bottle, in order to get sufficient weight of 

 water to force itself rapidly through the strainer. If the holes are 

 made near the top of the vessel, it will not work much more rapidly 

 than the Wright's form, although even in that case the absence of 

 funnels is a great convenience. 



Cleaning Diatoms.* — ICr. K. M. Cunningham gives some addi- 

 tional hints as to the application of bisulphate of potassa in cleaning 

 diatoms which is applicable to the treatment of nearly all varieties of 

 diatomaceous material : — 



" Proceed as follows. 



Crush to powder a few crystals of the bisulphate of potassa, and 

 add to it a proportionate quantity of the material to be cleaned, mix 

 intimately together, and transfer it to a hollow space practised in the 

 end of a sound piece of charcoal. Then with the blowpipe direct 

 the flame of a candle upon the mixture, when a violent boiling up 

 will ensue, and when it finally ceases to fuse readily, when the 

 potash appears opaque and of a whitish colour, it is to be removed 

 and dropped into a thimbleful of water, and boiled a few seconds ; 

 the potash dissolves readily, and liberates the sand and diatoms in a 

 cleaned state. After settling in a shallow porcelain saucer, draw off 

 all the water and collect the diatoms into the smallest compass 

 possible, and transfer them to a nickel ; take the nickel in the wire 

 tongs, and dry with blowpipe flame ; it will dry immediately, and the 

 diatom powder is to be scraped off and put aside for use. 



All the requisites for the above process consist of a co mm on 

 dime blowpipe, small wire tongs, 6 inches long, to hold the thimble, 

 nickel, &c., a pocket coin, a brass thimble, a few pieces of sound 

 charcoal, a candle, and a small supply of the bisulphate of potassa. 



When the bisulphate cannot be readily procured, an admirable 

 substitute may be found in the following, viz. common powdered 

 sulphate of potash, and a small quantity of sulphuric acid, both of 

 which are always found in prescription drug-stores. In using these 

 materials, the diatoms to be cleaned are mixed with an equal quantity 

 of the powdered sulphate of potassa, and a few drops of sulphuric 

 acid are mixed with it ; it solidifies at once, and can be broken into 

 suitable pieces to be fused on the charcoal, as before described. The 

 superior advantages of the process here described will become 

 apparent to those who have tried the acid methods of cleaning." 



In a subsequent note J the same author says : — 



" The following process is the result of a recent fortuitous 



* Amer. Mon. Micr. Journ., ii. (1881) p. 93. t Ibid., p. Hi. 



