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_ Method of making Ship Lanterns with Mica and iVire. 133 
tum. This method completely answered the purpose; but hav- 
ing observed that this oil gave out a strong and disagreeable 
smell, and that it evaporated too quickly, he conceived that the 
different essences extracted from vegetables, without being at- 
tended with the same inconveniences, might give to paper a 
sufiicient degree of transparency to allow a drawing upon which 
it might be laid to be distinctly seen through it. 
For this purpose he employed essence of lavender, or oil-of 
spike, and essence of citron, which are preferable to oil of petro- 
Jeum; because instead of having a bad smell they yield a very 
agreeable perfume : and as they evaporate more slowly, the 
paper retains its transparency for a greater length of time, by 
which means the operation of copying is facilitated. 
The essences used for this process ought to be as limpid as 
the purest water. If they were coloured, they would leave marks 
and stains upon the paper. They are rarely to be met with im 
commerce in a state of sufficient purity; but they may be easily 
freed front their colouring particles by a second distillation. 
Take a sheet of common drawing paper, and smear it on one 
side only with a brush dipped into the essence. The space thus: 
rendered transparent should be about seven or eight decimetres 
square ; for, if it be much larger, the essence may evaporate be- 
fore the drawing is finished, and the paper lose its transpa- 
rency. 
This done, lay the paper upon the drawing, and trace with 
the pencil the strokes that are seen underneath. Having copied 
the drawing upon that part of the paper which has been smeared 
with the essence, rub it upon the other parts, and thus proceed 
till the whole is finished. Then hold the paper before the fire, ° 
shaking it gently to accelelate the evaporation ; taking care that: 
it be at such a distance that the hand can bear the heat without 
inconvenience. When the evaporation is completed, the paper 
again becomes opaque, and retains all its eriginal whiteness. You 
may then draw upon it with a pen, wash or paint with colours. 
The process is as easy in practice as it is advantageous, on ac- 
count of the time which it saves, and the precision and accuracy 
with which you obtain fac-similes of prints and drawings that 
you wish to copy. « 
XXXI. On a Method of making Ship Lanterns with Mica 
and Wire. By M. Rocnon *. 
Tue great fragility of glass does not allow of its being employed 
in every sort of lantern, lamp, &c. In the navy it is necessary 
* From the Annales des Arts ct Manufactures. ; 
13 that 
