I90 Answers to Querzes. 
Red Copying-Ink.— Dissolve 50 parts of extract of logwood 
with 750 parts of distilled water in a mortar and without the 
application of heat. Add 2 parts of chromate of potassium, and 
set aside for 24 hours. Then add a solution of 3 parts of oxalic 
acid, 20 parts of oxalate of ammonium, and 4o parts of sulphate 
of aluminium, in 200 parts of distilled water, and again set aside . 
for 24 hours. Boil in a bright copper vessel, add 50 parts of 
vinegar, and after cooling bottle it; cork well. After a fortnight 
decant the clear liquid. The ink writes well, gives brownish 
copies, and turns darker on the paper. 
A Good Mucilage.—Take 400 parts of dextrine and stir into 
400 parts of water, then add 200 parts more water. To this add 
20 parts glucose, to parts aluminium sulphate. Heat the mixture 
to 195° F. Then the mixture becomes thin and transparent. 
V. A. LATHAM. 
Preservative for Books.—Vaseline, well rubbed in, prevents 
the leather from cracking and rubbing, and it preserves calf, 
morocco leather, and cloth, also marbled and gold edges, but 
not so well. V. As ES 
Answers to Queries. 
359.—Thorax.—I have a transverse section of foetal thorax, 
showing spinal cord, lungs, liver, and adjacent parts zz situ. It 
was prepared as follows :—Transfer the portion to be cut from 75 
per cent. alcohol to absolute for several weeks ; then into absolute 
alcohol and sulphuric ether, equal parts, for a few days; then toa 
moderately thin solution of celloidin in equal parts of absolute 
alcohol and ether, remaining tightly corked up for several months ; 
then into a thicker solution of celloidin for a few weeks; then 
hardened and cut in the usual manner for celloidin preparations. 
Stain sections in borax carmine, put into 95 per cent. alcohol, 
cleaned by dipping a few moments into common commercial car- 
bolic acid, which serves an excellent purpose, and will rapidly 
clean a section taken from 80 per cent. alcohol, so that it will 
mount clear in balsam without affecting the celloidin which holds 
the parts in place. By the use of celloidin, one can mount 
sections of flowers, ovaries, etc., with every part 7 sztu. V. A. L. 
395.—Infinite Series.—In my reference to the Binomial 
Theorem (p. 175), two errors occurred in the printing of the 
third term. It should have been: n (n—1) x’/2!. The index 2 
was misprinted r, and the solidus, or symbol of division (!), misin- 
terpreted as one of multiplication. The note of admiration after 
a symbol, such as 2 !, 3!, ~!, etc., stands for “‘factorial” 2, 3, or #, 
