352 THE YOUNG 
drawing, etc., the bichromate will be unchanged, 
and hence capable of forming chromate of silver, 
which is insoluble in water. If dried hy the fire, 
the picture will remain red ; but if exposed to the 
sunlight, it becomes darlc brown. Sulphuretted 
hydrogen, or a bath of potash and copper turns it 
hlsxGk.—Comptes Bendus. 
Jrattital Jiiits. 
—A soft alloy, which attaches itself so firuily to 
the surface of metals, glass, and porcelain tluit it 
can be employed to solder articles that will not 
bear a very high temperature can, it is said, be 
made as follows: Copper dust obtained by pre- 
cipitation from a solution of the sulphate by 
means of zinc is put in a cast-iron or porcelain- 
lined mortar and mixed with strong sulphuric 
acid, specific gravity 1.85. From 20 to 30 or 36 parts 
of the copper are taken, according to the hardness 
desired. To the cake formed of acid and copper 
there are added, under constant stirring, 70 parts 
of mercury. When well mixed the amalgam is 
carefully rinsed with warm water to remove all 
the acid, and then set aside to cool. In 10 or 12 
hours it is hard enough to scratch tin. If it is to 
be used now, it must be heated so hot that when 
worked over and brayed in an iron mortar it be- 
comes as soft as wax. In this ductile form it can 
be spread out on any surface, to which it adheres 
with great tenacity, when it gets cold and hard. 
—A man can always learn something if he will 
only look about him. I was at the Postoffice 
Department the other day, says an observer, and 
I noticed an employee busy affixing stamps to en- 
velopes. Every time he moistened the right 
hand corner of the envelope and then placed the 
stamp upon it. I asked him if there was any ad- 
vantage in wetting the envelope instead of the 
stamp, and he said: " You notice that I moisten 
the envelope first; well I do that because it is the 
right way. There is a right and a wrong way to 
everything, and consequently there is a right 
and a wrong way to put on postage stamps. It is 
impossible to moisten a stamp with the tongue 
unless a small proportion of the gum adheres to 
it. Now this gum is by no means injurious, but 
then the department does not advertise it as a 
health food; so the only way left is the right way, 
and that is to moisten the envelope first." After 
listening to this brief statement I felt a,s t hough 
I had emerged from the deep shade of ignorance 
to the glorious sunlight of knowledge. 
—Men, women and children require just so 
much sleep, and if they do not have it, suffer in 
consequence. I do not think a person should be 
waked in the morning, and for this reason, when 
a man falls asleep, he is in the shop for repairs, 
as the railroad men say. His frame and all its 
intricate machinery is being overhauled and 
made ready for the next day's work. The wear 
of the previous day is being repaired. Nature is 
SCIENTIST. 
doing that herself. She knows what the tired 
fra,me needs just as she knows how to make the 
heartthrob and send the blood coursing through 
the veins. Then she takes that tired frame, lays 
it down on a bed, surrounds it with the refreshing 
air of night, covers it with the soft darkness, and 
lets the man rest. " Tired nature's sweet re- 
storer, balmy sleep," visits him, and as the hours 
wear by, his energies are renewed, his strength 
comes back, and finally, when morning breaks 
and the sunlight steals through the lattice, he 
opens his eyes and is himself again. Or, if he is 
early to bed, he awakes with the cock's crowing. 
Now, who shall go to that man's side an hour be- 
fore he opens his eyes, and say to nature, stand 
aside and let him get up ; he has had enough of 
rest? Well, nature will say: "You can take 
him if you will, but I will charge him with an 
hour's loss of sleep, and I'll collect it out of his 
bones and nerves, and his hair and eyesight. 
You can't cheat me. I'll find property to levy 
on ! ''—Journal of Health. 
Ilotts luib %m'm. 
In continuing this depai tmeiit, which has been found of 
so much vahie, we would remind our readers who wish for 
information on any of the arts and sciences, that they are 
cordially invited to make their wants known through this 
column, and those of them who can furnisli accurate 
answers to questions asked are requested to send in replies. 
Doubtless many of our subscribers may know of methods, 
processes, or devices that may be better or more suitable for 
the particular case in question than anything generally 
known, and it is this reason that induces us to keep this de- 
partment open for a medium, where an interchange of ideas 
and practices may be made to the advantage ot all our 
readers. Correspondents will please send their full address 
when forwarding their communications — either questions or 
answers — not for publication, unless expressly so stated, but 
so that we may know wliere to find the wiiterif desirable. 
Communications should be sent in on or before the first of 
each month previous to publication^ to insure insertion in 
next issue. 
Answers. 
133. New Hampshiee Boy.— Concrete is the best 
building material in the world. It is four times 
cheaper than wood, six times cheaper than 
stone, and superior to either. Proportions for 
mixing: to eight barrows of slaked lime, well 
deluged with water, add 15 barrows of sand ; mix 
these to a creamy consistency, then add 60 bar- 
rows of coarse gravel, which must be worked 
well and completely; you can then throw stones 
into this mixture, of any shape or size, up to ten 
inches in diameter. Form moulds for the walls of 
the house by fixing boards horizontally against 
upright standards, Avliich must be immovably 
braced, so that they will not yield to the immense 
pressure outwards as the material settles: set the 
standards in pairs around the building, where 
the walls are to stand, from six to eight feet 
apart, and so wide that the inner space shall form 
the thickness of the wall. Into the moulds thus 
formed throw in the concrete material as fast as 
you choose, and the more promiscuously the 
better. In a short time the gravel will get as hard 
as the solid rock.— Euby. 
134. Weathekwise.— There is no valid reason 
why you should not be able to construct a toler- 
ably correct barometer if you follow the direc- 
tions given herewith: Get a strong glass tube 34 
inches long and of a smooth even bore. Close 
one end by means of a spirit lamp and blow 
