De Lautour. — On a Diatoynaceous Deposit. 299 



drop or two of water. The exact proportion is 5 c. centimetres 

 of water to 100 c.c. of the salt. Heat in a water-bath. Just 

 before reaching the boihng-point the salt will melt and be 

 absorbed by the earth. Allow it to remain about ten minutes 

 in the bath — a little longer will not do it any harm (I find 

 that taking it out of the bath and giving it a good boil 

 assists materially) — then allow it to cool. When quite cool 

 add a fragment of the crystal acetate of soda, when 

 the whole will immediately crystallize. Let it do so 

 thoroughly. Then add water in excess. Heat and empty 

 into a large and suitable vessel, and add quantities of water 

 to wash out the acetate. I find boiling water is the best, and 

 that the process is much facilitated by the addition of a small 

 quantity of hydrochloric acid. If necessary the process may 

 be repeated. It may be as well to observe that in this, as in 

 all the other washings, the great thing is plenty of water and 

 plenty of patience. Working at it for an hour or two a day, 

 you will be fortunate if you have got your diatoms thoroughly 

 clean in a week. 



Many works relate various methods of cleaning diatom 

 earth, but the methods are somewhat intricate and the direc- 

 tions somewhat vague. It was not until Mr. Joseph Stevens, 

 of 18, Conference Street, Christchurch, came on a visit to 

 Oamaru and showed us his method that we were able to work 

 satisfactorily. And I may say I have never seen better 

 specimens of mounting than those given me by Mr. Stevens. 



Mr. Stevens's method is first boiling the disintegrated earth 

 with strong sulphuric acid — the strongest possible. After boil- 

 ing a few minutes add cautiously small quantities of chlorate 

 of potash while boiling. The quantity of H2SO4 used is 

 about twice the quantity of earth to be acted on, which must 

 contain as little moisture as is conveniently possible. The 

 boiling is continued until the earth becomes either brown or 

 pitch-black, which depends on the quantity of organic matter 

 in it, and the consequent charring or carbonising of the 

 organic dirt. The chlorate of potash is added while boiling, to 

 bleach the earth. (Some authors recommend permanganate 

 of potash as being safer.) The oxygen unites with the carbon, 

 and in a short time the blackened earth is as white as snow. 

 This process, which is conducted in a large test-tube, is the 

 first step, and you will succeed better by not attempting to 

 work with too much earth at a time — a teaspoonful, or even less, 

 is quite enough. And I would caution you to be very careful 

 when first bringing the sulphuric acid to a boil. Do not be in a 

 hurry — bring it by gentle degrees to a boiling-point ; for some- 

 times it is jumpy, and will suddenly explode out of the test- 

 tube, to the ruin of your table, clothes, and hands. This can 

 be entirely obviated by patience. Eemember also that the 



