The play that occurs between this conical slide and the stops
varies according to the position of the former.
[Illustration: RULER AND TRIANGLE FOR HATCHING.]
The apparatus operates as follows: In the figure, the stop to the right
being in contact with the piece, D, a line is drawn along the right side
of the triangle. Then the ruler is made to slide along the triangle until
D touches the other stop, and then the triangle is slid along the ruler
until the stop to the right touches D again. In this position another
line is drawn, and so on. The position of the piece, D, between the stops
is regulated according to the fineness of the hatching to be
done.--_Chronique Industrielle_.
* * * * *
THE DISTILLATION OF SEA WATER.
The supplying of the troops at Suakim and in the Soudan with water is one
of the most important items in the whole conduct of the Egyptian war.
Even in cold or temperate latitudes fresh water is a first necessity for
animal life; much more is this the case in the desert; and the wells in
the country forming the scene of our military operations form in
themselves valuable strategical points. Their supply, however, has to be
supplemented, and to do so artificial means and the aid of the engineer
have to be enlisted into this service.
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