BLAZE-CURRENTS OF VEGETABLE TISSUES. 33 
A with a finger of the other hand; when the galvanometer-spot 
flies off to my right. 
$2. The galvanometer, being in a strange place, must now 
be calibrated by means of the compensator. Here are the 
calibration-numbers taken at the outset of the present obser- 
vations :— 
August 4th.—Galvanometer of 7000 w R. 
Compensator, Deflection. 
— 0:001 +0:001 — Sem, + 3cm. 
—0:002 +0002 —6, +6, 
— 0:003 4- 0:003 —9 , + 9 ,, 
— 0004 4-0:004 —]12 , +12 , 
—0:005  +0-005 —15 , 15 , 
Swing 8 
Steady Deflection 2 
One double oscillation = 7 secs. 
Quite at rest in 30 secs., after 4 double oscillations. 
The instrument is now sufficiently adjusted for our purposes ; 
the fact that it is not very sensitive (1 em. deflection indicating 
rather less than 1077 ampère) is an advantage under our present 
circumstances, 
A photograph of the Laboratory corner as it stands at the end 
of the first day shows the apparatus unpacked and set up ready 
for use (fig. 1, p. 34). 
A diagram of the circuit is seen to the right; the apparatus 
itself—galvanometer, seale, shunt, electrode-holder A B, cells, 
compensator, coil, reversers, keys, and, in the foreground, the 
keyboard—is arranged on the packing-case, and is not much 
more bulky or troublesome to pack and unpack than a dressing- 
bag. As a travelling nécessaire, I regard it as quite indis- 
pensable ; and it serves to demonstrate that electro-physiology 
can be studied elsewhere than in beautifully-arranged Institutes 
of Physiology. 
I have often described the use of the various parts of the 
apparatus; and we shall see in the next few days what can be 
done with it. I shall not now redeseribe it; all I shall do will 
be to say that the photograph exhibits two additional pieces on 
the travelling-box, to the right and left of the electrode-holder 
(which are not represented in the diagram), and to make a 
remark intended to guard against any misunderstanding as to 
the * voltage " of physiological currents. 
“LINN. JOURN.—BOTANY, VOL, XXXVIT. D 
