structureless as albumen slides, without the great trouble involved in
making them. You must not accept the slides put before you this evening
as the best that can be done with gelatine. Far from it; they are only
the work of an amateur with very little leisure now to devote to their
manufacture, and are merely the result of a series of experiments which,
so far as they have gone, I now place before you.--_Thomas Mayne, T. C.,
in British Journal of Photography._

* * * * *




AN INTEGRATING MACHINE.

[Footnote: Read at a meeting of the Physical Society, Feb. 26.]


By C.V. BOYS.

All the integrating machines hitherto made, of which I can find any
record, may be classed under two heads, one of which, Ainslee's machine,
is the sole representative, depending on the revolution of a disk which
partly rolls and partly slides on the paper, and the other comprising
all the remaining machines depending on the varying diameters of the
parts of a rolling system. Now, none of these machines do their work
by the method of the mathematician, but in their own way. My machine,
however, is an exact mechanical translation of the mathematical method
of integrating y dx, and thus forms a third type of instrument.