THE YOUNG SCIENTIST. 
129 
perspective, and will call for a good deal 
of ingenuity and skill to master them per- 
fectly. 
By a proper study of our model plate, 
(where the originals cannot be procured) 
the ability to draw objects from nature 
may be cultivated. The student will find 
more difficulty in this than in merely 
copying lines already laid down, un- 
less he understands what we have taught 
in the former lessons, which are but as 
the alphabet to be used in connection with 
the laws of perspective, to determine 
nature, and present in your work a mirror 
of truth. 
Mysterious Clocks. 
THEEE is at the present time quite a 
furor for mysterious or magic clocks 
which shall puzzle the observer to tell 
how they are driven. One of the simplest 
and best is that shown in the engraving. 
The clock apparently consists of a square 
plate of glass which is suspended by cords, 
so as to be entirely unconnected with any 
mechanical source of power. On this 
MAGIC CLOCK. 
plate are marked the figures for hours 
and minutes, and attached to the centre 
are two hands which move round the dial 
and point to the time with considerable 
accuracy. A very curious feature of this 
clock is the fact that the hands seem to 
turn loosely on the central point, and if 
twirled around any number of times, will 
settle back to the right place, even mak- 
ing allowance for the few seconds in w^hich 
they have been moving. They may also 
be taken off and laid away for some hours, 
and when again placed in position, they 
will indicate the correct time. 
The secret of this clock lies in the coun- 
terpoises attached to the hands. These 
counterpoises contain the works, and the 
positions of the hands are determined by 
weights which these works move out 
and in from the centre, thus giving the 
weights greater or less leverage, and 
causing the hands to act in the same way 
as the well-known bent lever balance. 

The New Copying Process. 
C OME time ago, a new method for rapidly 
^ producing copies of letters, or any 
kind of written matter, was made the 
basis of a patent in Austria. The sim- 
plicity and facility of working the ap- 
paratus immediately attracted universal 
attention, but the high price of the first 
apparatus was not at all in proportion to 
the cheap materials, even allowing for a 
very respectable profit. It was soon as- 
certained that the process, or rather the 
composition of the printing material, was 
not capable of being patented, being noth- 
ing else than gelatine (or glue) and 
glycerine. Since then, in Europe as well 
as in the United States, a number of 
such apparatus, have made their appear- 
ance under various names, such as Copy- 
graph, Copygram, Hectograph, Litho- 
gram, Cheirograph, Autograph, Multi- 
graph, etc. Competition has so reduced 
the prices of these that they are now sold 
at not unreasonable rates, and many will 
prefer to buy them ready made with all 
the necessary appliances. But for those 
who wish to make an apparatus for them- 
selves, we append several methods : 
1. Take one part by weight of gelatine 
(glue does just as well), let it swell in two 
parts of water, melt, and add four parts of 
(common) glyceriae, with a few drops of 
carbolic acid, and sufficient whiting or 
white lead to make the whole milky. 
Pour the mixture into a shallow tin or 
zinc dish ; it will be ready for use in about 
twelve hours. 
2. Ten parts of gelatine are softened 
in water, and then dissolved in 100 parts 
of concentrated glycerine, on the water- 
bath. When melted, the mass is slowly 
and carefully poured into a tin-tray, about 
k cm. (i-l inch) deep, and of any desired 
