31/2 2 2-7/8
31/2 21/2 21/2
31/2 3 13/4

4 2 31/2
4 21/2 3-1/8
4 3 2-5/8
4 31/2 2

5 3 4
5 4 3

For larger ovals multiples of these numbers may be taken; thus for 7 and
4, take from the table twice the width corresponding to 31/2 and 2, which
is twice 2-7/8, or 53/4. It will be noticed also that columns 2 and 3 are
interchangeable.

To use the apparatus in connection with the table: Find the length of
the desired oval in the first column of the table, and the width most
nearly corresponding to that desired in the third column. The
corresponding number in the middle column tells which hole the needle
must be passed through. The tack D, _around_ which the string must pass,
is so placed that the total length of the string AD + DC, or its equal
AE + EC, shall equal the greater diameter of the ellipse. In the figure
it is placed 61/2 inches from A, and 11/2 inches from C, making the total
length of string 8 inches. The oval described will then be 8 inches long
and 61/4 inches wide.

The above table will be found equally useful in describing ovals by
fastening the ends of the string to the drawing as is recommended in all
the text books on the subject. On the other hand, the instrument may be
set "by guess" when no particular accuracy is required.

* * * * *

THE MANUFACTURE OF CHARCOAL IN KILNS.

The manufacture of charcoal in kilns was declared many years ago, after
a series of experiments made in poorly constructed furnaces, to be
unprofitable, and the subject is dismissed by most writers with the
remark, that in order to use the method economically the products of
distillation, both liquid and gaseous, must be collected. T. Egleston,
Ph.D., of the School of Mines, New York, has read a paper on the subject
before the American Institute of Mining Engineers, from which we extract
as follows: As there are many SILVER DISTRICTS IN THE WEST where coke
cannot be had at such a price as will allow of its being used, and where
the ores are of such a nature that wood cannot be used in a
reverberatory furnace, the most economical method of making charco