ical facts as there can be to this. At all events free and
open discussion of all natural and moral phenomena must lead to
truth at last. Is Babbage the author? I rather think he would not be
so careful in concealing his name....

[My mother made some curious experiments upon the effect of the
solar spectrum on juices of plants and other substances, of which
she sent an account to Sir John Herschel, who answered telling her
that he had communicated her account of her experiments to the Royal
Society.]

* * * * *

SIR JOHN HERSCHEL TO MRS. SOMERVILLE.

COLLINGWOOD, _November 21st, 1845_.

MY DEAR MRS. SOMERVILLE,

I cannot express to you the pleasure I experienced from the receipt
of your letter and the perusal of the elegant experiments it
relates, which appear to me of the highest interest and show (what I
always suspected), that there is a world of wonders awaiting
disclosure in the solar spectrum, and that influences widely
differing from either light, heat or colour are transmitted to us
from our central luminary, which are mainly instrumental in evolving
and maturing the splendid hues of the vegetable creation and
elaborating the juices to which they owe their beauty and their
vitality. I think it certain that heat goes for something in
evaporating your liquids and thereby causing some of your phenomena;
but there is a difference of _quality_ as well as of _quantity_ of
heat brought into view which renders it susceptible of analysis by
the coloured juices so that in certain parts of the spectrum it is
retained and fixed, in others reflected according as the nature of
the tint favours the one or the other. Pray go on with these
delightful experiments. I wish you could save yourself the fatigue
of watching and directing your sunbeam by a clock work. If I were at
your elbow I could rig you out a heliotrope quite sufficient with
the aid of any common wooden clock.... Now I am going to take a
liberty (but not till after duly consulting Mr. Greig with whose
approbation I act, and you are not to gainsay our proceedings) and
that is to communicate your results in the form of "an extract of a
letter" to myself--to the Royal Society. You may be very sure that I
would not do this if I thought that the experiments were not
intrinsically quite deserving