10 
THE YOUNG SCIENTIST. 
heard of people who denounced as a fraud an inch 
lens because it was claimed to magnify ten times ! 
In our next issue we will take up the subject of mag- 
nifying power, and the best way to measure it. 
A New Slide for Microscopic Objects. 
Mr. D. Bryce Scott, Curator of the New York 
Microscopical Society, has devised a very simple 
and ingenious slide, by which opaque microscopic 
objects may be mounted easily, quickly and well. 
The usual methods, as many of our readers know, 
is to make a cell on a glass slide— a tedious and 
comparatively difficult process, when a cell of some 
way is very friable, and must be kept packed in cot- 
ton wool when not in use. To get rid of this fragile 
character, Dr. Hare dipped asbestos, first in a solu- 
tion of bichloride of platinum, and then in one of 
sal ammoniac, and found that the asbestos so pre- 
pared ignited hydrogen readily. But asbestos is 
not easily managed. We have succeeded admir- 
ably with pumice stone, which we first form into a 
cylinder of the proper size — say three-eighths of an 
inch in diameter — and then cut into discs about the 
twentieth of an inch thick, by means of a fine saw. 
These discs are soaked for some time in a strong 
solution of bichloride of platinum in alcohol, and 
afterwards for an equal period in a solution 
of sal ammoniac. After being ignited, these 
discs inflame a jet of hydrogen readily, and 
we find that they retain their power quite as 
well as the more delicate forms in common use. 
METAL SLIDE FOK OPAQUE OBJECTS. 
depth is required. The slide devised by Mr. Scott 
is of thin sheet metal (brass or tin), and is stamped 
so as to have a central depression, which forms the 
cell, and a turned down edge all round it which 
gives it strength, and causes it to lie steadily on 
any flat surface. The cell has a ledge, or rebate, 
as seen iu the lower figure, for the purpose of sup- 
porting the thin glass cover. When made of tin 
the whole slide is japanned; those made of brass 
are lacquered, and the interior of the cell is covered 
with black asphalt, or some similar dark varnish. 
The objects are attached to the surface of the 
varnish by means of gum water, to which a very 
little glycerine has been added, and the thin glass 
cover may be cemented down and varnished on the 
turn-table in the usual manner. The simphcity 
and efficiency of this slide leads us to believe that 
it will become a general favorite. 
Self-Lighting Lamps. 
The well-known property possessed by some 
forms of platina, whereby it instantly ignites a 
stream of hydrogen, has long been utilized in the 
construction of self-lighting lamps. A few years 
ago these lamps came into great favor as a substi- 
tute for matches, from the fact that they were free 
from the fumes of sulphur, and there was no dan- 
ger of rats or mice causing unexplained fires. The 
usual method of forming spongy platina into a 
mass to be used in igniting hydrogen, is to mix it 
with fine clay and mould it on a frame work of 
platinum wire. Platinum sponge prepared in this 
Home-made Telephone. 
Prof. Barrett, in a recent lecture on the tele- 
phone, gave a receipt for making a cheap one. 
Take a wooden tooth-powder box, and make a 
hole about the size of a half-crown in the lid and 
the bottom. Take a disc of tinned iron, such as 
can be had from a preserved meat tin, and place 
it on the outside of the bottom of the box, and 
fix the cover on the other side of it. Then take a 
small bar-magnet, place on one end a small cotton 
or silk reel, and round the reel wind some iron 
wire, leaving the ends loose. Fix one end of the 
magnet near, as near as possible without touching, 
to the disc, and then one part of the telephone is 
complete. A similar arrangement is needed for the 
other end. The two are connected by the wire, and 
with this Prof. Barrett says he has been able to 
converse at a distance of about 100 yards. — Nature. 
Lead, in Paraffin Oil. — It has recently been 
found that paraffin oil, which is very similar to our 
petroleum, is capable of taking up a large per- 
centage of lead. 
Poisoned by Cheap Jewelry. — Two young 
girls in Paris were severely afflicted with sore 
eyes. Medical aid proved entirely ineffectual, until 
their cheap ear-rings, which doubtless consisted 
largely of copper, were removed. 
Silk-Worms at Large.—Between San Jose 
and Santa Clara there are large quantities of silk- 
worms at large. They are understood to be from the 
old stock of M. Provost. They multiplied on the 
poplar trees, and then attacked the fruit trees, so 
so that a fruit grower near by was forced to dose 
