Advantages of the Crescograph.—There is no existing
method which enables us to detect and measure such infinitesi-
mal movements and their time-relations. The only attempt
made in measuring minute growth has been by observing
the movement of a mark on a growing plant through a
microscope. The magnification available in practice is about
.‘350 times. The observation of the movement would itself
be sufficiently fatiguing. But a simultaneous estimate of the
time-relations of' rapidly fluctuating changes would prove
so bewildering, that accurate results from this method would
be altogether impossible. A 1'2" objective gives a linear en-
largement. of about 1,200 times. But the employment of this
objective is impracticable in the measurement of growth
elongation of an ordinary plant. With the Crescograph, on
the other hand, we. obtain a magnification which far sur-
lube-«'5 the highest powers of a microsc0pc, and it can he
used [or all plants. it does not merely detect growth but
automatically records the rate of growth and its slightest
fluctuation. The extreme shortness of? time required for an
experiment renders the study of the influence of’ a single
factor at a time possible, the other conditions being kept
constant. The. (ll-escograph thus Opens out a very extensive
field of inquiry into the physiology of growth; and the dis-
covery of several important phenomena mentioned in this
Paper is to be ascribed to the extreme sensitiveness ot‘ the
appa'atus, and the accuracy of the method employed.
MAGNJTIC AMI’LIFIC ATION.
'l‘he magnification obtained with two levers was, as stated before. 10,000 times. It may be thought. that further magnification is possible by a compound system of three levers. There is, however. a limit to the number of levers that may be employed with advantage, for the slight over- Weight of the last lever becomes multiplied and exerts very
