532 SUMMARY OF CURRENT RESEARCHES RELATING TO 



student, who finds his beautiful diatoms — after all the acid treatment 

 and all the incineration — yet full of flocculent matter, that there is a 

 royal way to cleanness, and, after all, the good old way, by the use of 

 soap ! In fact, the use of this common and too much neglected 

 article will produce astonishing changes in cleaning up the diatoms, 

 as well as in cleansing dirty linen. I will describe what I did yester- 

 day — the whole during one evening, and in fact, except for the waiting 

 for the diatoms to settle, all the process would not occupy over ten 

 minutes. I received a gathering of marine diatoms from the Hawaiian 

 Islands, enclosed in a joint of bamboo instead of the usual vial. They 

 were dried and matted, but the gathering was rich in the well-known 

 Sandwich Island forms, so characteristic that I could have told the 

 locality if I had not already known, 



I put the dried material, such as it was, into a large test tube, 

 and covered it well with nitric acid and left it for an hour (the time 

 is not material). After this I boiled it, adding a little more acid, and, 

 dropping in two small bits of bichromate of potassa, again boiled for 

 a minute or two. The tube was now filled with rain water, and the 

 whole mixed by inverting, &c. As soon as the mass (flocculent 

 enough) had settled, the discoloured and acid water was poured ofi", 

 and the tube was again filled with rain water (it is better to use soft 

 water). After settling, the water was again poured ofi* and the deposit 

 once more washed. So far this is the old method, which generally 

 ends here, only washing out as best one can the lighter forms and 

 broken frustules. A preparation made at this stage, marked (1) on 

 the slide sent herewith, showed plenty of diatoms, principally Synedra 

 robusta an:l Bhahdonema mirificum, but also any amount of the floccu- 

 lent matter — the bane of diatom j^reparers, and which, from presence 

 still of organic matter, browned in burning ; a subsequent washing 

 somewhat improved this — see specimen marked (2). Pouring off the 

 supernatant water, and adding a little clean soft water, I now put into 

 the tube a bit of common yellow soap, size of a pea, and again boiled 

 the deposit for a minute or two, after which the tube was filled with 

 clean rain water. Some fifteen or twenty minutes after, the yet milky 

 fluid was poured off; it contained but few and very minute diatoms, 

 which one can save, if so disposed, by keeinng the poured-off fluid for 

 a longer time. The tube, with a heavy deposit at bottom, was again 

 filled with rain water and shaken, and now a peculiar brilliant spark- 

 ling and play of colours showed that the flocculent matter was gone, 

 and only clean diatoms, sponge spicules, and possibly some sand 

 remained. Specimen marked (3) shows aj^pearance at this stage, 

 and that marked (4) after one more washing. Finally, distilled 

 water and alcohol was added ; and after this washing, pouring off all 

 the finer forms which remained in suspension after five minutes, 

 and which were saved with those of the other washings, little else 

 remained except clean diatoms, as shown on the finished slide sent 

 herewith. 



If, after this, any one exhibits a slide of diatoms full of floc- 

 culent and dirty deposit, peculiar to the old methods of treatment 

 (unless, indeed, the original gathering had been an exceptionally 



