708 SUMMARY OF CURRENT RESEARCHES RELATING TO 



in most cases, the only method used after the boiling and washings. 

 I have a slide of polished glass 3^ inches by 4^ inches ; a smooth block 

 of wood 4 inches by 5 or 6 inches, and 3 inches thick ; two wide- 

 mouth bottles of 4 to 6 ounces capacity, with thin, projecting lips, 

 one empty, the other filled with the material thinly diffused in 

 water ; several pieces of considerable size of old worn cotton-cloth, 

 and, for I like it best, a clean linen pocket-handkerchief, and a small 

 table. The table I place beside my wash-bowl, which is supplied 

 with water — not filtered in this instance — through a pipe and faucet, 

 and on it are arranged my bottles, block, and cloths. I place the 

 glass slide on the block, taking care that the latter is level, and, 

 well shaking the material, pour a little of it on the slide, and then 

 quickly pour it off, tipping the slide so that the material will flow off 

 from a corner of it into the empty bottle. The diatoms float off into 

 the bottle, and the sand adheres to the slide. The slide is then 

 washed by letting water upon it from the faucet, then wiped as well 

 as may be with one of the large pieces of cloth, and then the surface 

 to be used is wiped with the linen handkerchief. This last wiping 

 dries the surface thoroughly, and removes any little shreds of cotton 

 which may have adhered to it from the cloth. Care is taken that none 

 adhere. In this way the material is all worked over, and this treat- 

 ment has to be repeated perhaps many times before the material is 

 sufficiently rid of the sand. It may be that before this is accom- 

 plished, the sand and diatoms will cling together on the slide, causing 

 considerable loss of the latter. This is owing to little particles of 

 matter getting into the material from the cloths, or from the air, and 

 cannot be prevented. As soon as this clinging is detected, which is 

 easily done by occasionally examining the slide under the Microscope, 

 first drying it after pouring off the material, the latter should be 

 boiled for a minute in sulphuric acid, to which is added a little 

 chlorate of potash while boiling. Of course the diffused material is 

 poured into a beaker, allowed to settle, and the water drained off. It 

 is then washed and the treatment continued. When the material is at 

 last freed of sand, it is boiled a last time in sulphuric acid, chlorate 

 of potash being used as before. It is then thoroughly washed and 

 properly diffused in dilute alcohol for mounting. The alcohol should 

 be filtered as well as the water. 



" In this last process some of the diatoms will adhere to the slide, 

 but this is of little consequence if there be plenty of material. As 

 the cloths get pretty wet, as they will, they should be exchanged for 

 dry ones." 



Modification of Paraffin-imbedding.* — The ordinary method of 

 imbedding delicate objects in paraffin is attended with so many 

 objections, such as the disagreeable shrinking, brittleness, and 

 fragility which the object shows by lying long in oil of turpentine or 

 in a warm solution of paraffin in oil of turpentine, that 0. Biitschli 

 endeavoured for some time to find a substitute for the latter. After 

 several experiments he found chloroform to be a very excellent sub- 



* Biol. Centialbl., i. (18S1) pp. 591-2. 



