140 HOW TO PBEPARE FOKAMINIFERA. 



and iron wire should not be used, as they are sure to rust, and rot 

 the gauze. 



For filtration, a similar cylinder, three inches in diameter and 

 three deep, with a thick wire or flange at the top, (made so that it 

 may rest on the ring of a retort stand), and a fine brass wire at the 

 bottom, will be found very useful. This is used by tying over the 

 bottom a sheet of good filter-paper, free from holes, and outside it 

 a piece of gauze or muslin to prevent the paper bursting through. 

 For very small quantities, broken test tubes may be used in the 

 same way. The funnel-filter, as I know to my cost, is not satisfac- 

 tory, being apt to burst, and its valuable contents to be thereby lost. 

 There are small glass cylinders to be had at the apparatus shops, 

 which answer well. 



If the preservation of the Polycystina, or larger Diatoms, in 

 any gathering is desired, the finest linen handkerchief should be 

 used for a bowl, as described ; but for all other purposes, the i8o 

 gauze is everything that can be desired. I have sometimes used 

 it double, crossing the threads diagonally. This gauze may be 

 obtained at most of the wire-workers who supply mills ; it is made 

 in Lyons.* 



The material from which fossil Foraminifera may be most 

 easily prepared, is, perhaps, chalk-powder. Many ways are 

 recommended for doing this, one text-book copying another, — 

 apparently without proving the process, but just hoping it may be 

 a success. One plan which I remember advised to get a piece of 

 chalk and to brush it gently in water; allow this to stand and 

 settle, then pour off the water and add fresh, and repeat as needed. 

 Finish by spreading the sediment on a slip to dry, and add Canada 

 balsam. Another recommended to get the fine powder found at 

 the base of a cliff by the weathering of its surface, and treat this 

 similarly with water. I have spent hours working each of these, 

 and other plans, with chalk from Dover, Gravesend, and elsewhere, 

 in which Foraminifera are known to abound, and never got any 

 satisfactory result ; so I gave up trying to obtain the Foraminifera as 

 hopeless. Since then, through the kindness of my friend, Joseph 

 Wright of Belfast, I have learnt how to go to work with success. 



The proper material, — the only material worth handling, — from 

 which to obtain the Foraminifera found in the chalk in a condition, 

 almost, if not quite, uninjured, is the powdery matter found in the 

 cavities of the flints which abound in the chalk, but especially in 



* Of course, where the Siliceous organisms only are wished for, the best way is 

 to treat at once with acid so as to dissolve everything else, after which, wash as for 

 Piatoms. 



