902 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
be turned around the cover, and tbe mounting is done. It will be 
found that the mounting is easy as compared with Canada balsam, for 
no turpentine is used, and as no sticky residuum is used the cleaning is 
also easy. I think that those who use it will be pleased with the results, 
and Canada balsam mounts be sent to the limbo.” 
The Rev. Father Thompson’s High Refractive Medium.* — Mr. 
E. M. Nelson, who some years back exhibited a beautiful slide of 
diatoms, mounted in a very dense medium by the Rev. Father Thompson, 
has now, through the kindness of that gentleman, been able to com- 
municate the recipe of the composition. He still has the same slide in 
his possession, and, so far as it is possible to judge, it has remained 
unaltered. He therefore begs to commend Father Thompson’s high 
refractive medium to the especial notice of the Quekett Club as the best 
thing that has been done in that direction. 
“ Take flower of sulphur, bromine, and arsenious acid in the pro- 
portions of 8, 10, and 12 respectively by weight. Dissolve the sulphur 
in the bromine with gentle heat in a thinnish test-tube about 6 in. long. 
Over a small Bunsen jet add small portions of the arsenious acid, boil, 
and let the condensed vapours of the mixture cool and fall down the 
sides again. Be very careful that these do not escape. If none of these 
have escaped, the proportions given will be correct; but if they do 
escape, probably a spot more bromine will have to be added to keep the 
mixture clear. 
No mechanical directions can be given beyond these. Success is 
very much like that of a cook in his preparations, and the eye and 
understanding must regulate the proceedings. When made, the mixture 
should be about the consistence of toffee, and much the same in appear- 
ance. It should be handled with a piece of platinum wire. The more 
arsenic the better, and a grain or two of the metal itself may be coaxed 
in towards the end so long as the mixture remains clear. If properly 
made this will last, so far as I know, for ever.” 
Substitute for Glass for Covers and Slides for the Microscope.! — 
Dr. A. M. Edwards writes : — “ I think the price of slides and covers for 
microscopic use is enormously high, and as they can be made of a sub- 
stance much cheaper, and at the same time possessing properties which 
glass has not, viz. being unbreakable, that it should be known. In 
using celluloid, which is wood rendered soluble in ether and alcohol 
with gum camphor, for films for microphotography, I was struck with 
some of its properties, that made me think it could be used in micro- 
scopy. It is transparent, almost as transparent as glass, unbreakable, 
the weight is very little, making it especially valuable when sending by 
post, and therefore occupying very little room, which can thus be dis- 
pensed with. It is strong as wood, and stronger, has no fibre, and can 
be cut readily with scissors. I really wonder that it has not been used 
before for slides and covers. It can be obtained with a ground surface 
as well as plain, and the cost, which is a great item, is next to nothing. 
Very thin celluloid films are commonly used for instantaneous coverers, 
and this can be employed for covers, whilst the thicker kind used for 
* Journ. Quekett Micr. Club, v. (1892) p. 123. 
t Science Gossip, 1892, pp. 235-6. 
