Sept. 28, 1871] 
NATURE 
433 

floats, and as it rises at G, the arm / is elevated. The crayon 
holder, being fixed on the balance at the fulcrum, 7 by two 
little screws, swings a little to the left, and the crayon 
which it carries with it makes a mark on the paper be- 
neath it, which mark indicates the rise of the barometer, 
or the increase of atmospheric pressure. If the pressure 
decreases, the pencil, of course, moves in the opposite 
direction, and shows the barometric fall. The roll of 
paper on which the record is made by. this automatic 
instrument is divided into rectangular parts, each one of 
which exhibits the atmospheric variations for twenty-four 
hours. At the end of every day this part of the roll is 
detached and put by to be bound up in book form in the 
records of the office in which the instrument is kept. 













1871 
4 
HB 
oat 
ET 
A 
AA 
er line is the Wet Bulb 

z AAA = 
: niall)” = 
Ba ii = = 
=] 
me: E MM = 
ce = AMATI = 
2 MERE | eee 
* BE * HN = 
Be MM = 
Me . 28 
NK = 
a TS 
is in = 
| : 


HAC 
AN 
Hh 
I Het 
10.—DRAPER’S PHOTOGRAPHIC REGISTFR OF BAROMETER AND TPERMOMETER AT NEW YORK, APRIL 28, 
FIG. 

The roll of paper is on a reel,'7, passing between two | 
rollers, g and 4, as seen in B (Fig. 9). 
By these perfectly simple devices, instead of obtaining 
only three daily recorded observations, the observer at 
every station gets a continuous and perpetual record for 
every second in the day. That is to say, instead of get- 
ting, as by the common barometer (observed three times 
a day), observations for three seconds in twenty-four 
hours, he gets them for as many seconds as there are in 
twenty-four hours, or 86,400, Thus it follows that the 
value of the self- registering barometer, as compared with 
the ordmary one, is as 86,400 to3! -Y =~ 
The marvellous accuracy and’ exquisite nicety with 
which all the observations forwarded to General Myer by 
the observers are marked ought to assure the public that 


nothing is wanting to give reliability to the published 
results and the “ probabilities” issued from his officers. 
A self-registering barometer, as well as other instruments 
HN NHI 
MAA 







aphic Register from Noon, December 11, 1870, half-inch per hour.) Two Thermometer and One Barometric Curve 

































































































































































































































































































































FIG. I1,—PHOTOGRAPH OF A STORM.—(Print from Photogr 
of equal sensitiveness, will be used by all the observer- 
sergeants. It is- scarcely possible for this invaluable 
instrumert to suffer derangement or to get out of order. 
A third most beautiful and sensitive self-registering 
