412 
NATURE 
Ae aie Ne 
[ Sep¢. 21, 1871 

of war. The telegraph is capable of indefinite utilisation. 
General Von Moltke, it is well known, conducted the late 
operations of the German army on the battle-fields of 
France sitting in the rear with his map before him, and 
his telegraphic operator at his side, keeping him in com- 
munication with all parts of the field. It has been fre- 
quently said by distinguished military men that the 
telegraph will be one of the most effective weapons in any 
war that may now occur. How necessary for the Govern- 
ment to keep up the efficiency of such a corps as that of 
which we have spoken ! 
As the organisation under General Myer now exists, the 
President and Secretary of War have a responsible mili- 
tary man at every important post in the country. Ifa 
warlike expedition appears on any part of our coast, 
causing a panic or stampede, there may be a thousand 
wild rumours of frightened message-senders. The Govern- 
ment, however, is in the receipt every eight hours (and 
can be in the receipt every hour if it wishes) of a reliable 


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FIG. 6.—SECTION OF GREEN’S STANDARD BAROMETER 
message from its own agent, who reports on his responsi- 
bility what he saw and knows to be true; and this 
observer will not leave his post until ordered to do so. 
As a mere Government police, therefore, the Signal Corps 
would be worth to the nation far more than it can ever 
cost, even if its operations should be more widely extended, 
as will speedily be done. 
Each sergeant is sent to the Signal Service school for 
instruction at Fort Whipple, Virginia, where he is imme- 
diately supplied with Loomis’s “ Text-book of Meteoro- 
logy,” Buchan’s “ Hand-book of Meteorology,” Pope’s 
“ Practical Telegraphy,” and the “ Manual of Signals for 
the United States Army,” together with all the instruments 
necessary for practical instruction. The books he must 
thoroughly master. He is required to cite once daily 
didactically, and to practise a certain time with the instru- 
ments. He is required to remain under tuition until con- 
sidered by the instructor competent to take charge of a 
station and perform the necessary duties, when he is 


ordered before a board, consisting of three army officers, 
for examination, when, if considered incompetent, he is 
returned to Fort Whipple for further instruction and 
practice. 
If, after a rigid examination, he is found capable, he is 
assigned to a station, and the necessary stationery and 
instruments furnished him (the latter consisting of the 
barometer, thermometer, hygrometer, anemoscope, ane- 
mometer, and rain-gauge), and instructions to make three 
observations daily, viz., at the time corresponding with 
735 AM., 4.35 P.M., and 11.35 P.M. Washington time, so 
that every observer at each station should be reading his 
instruments at the same moment, and in the following 
order, viz, Ist, barometer ; 2nd, thermometer; 3rd, hy- 
grometer ; 4th, anemoscope; 5th, anemometer; and 6th, 
rain- gauge. 
In addition to the duties discharged by the officers of 
the Examining Board, Colonel Mallery, A.S.O., has the 
general charge of the very large correspondence of the 
office ; Captain Howgate has charge of the statistics and 
all observations of the service; and Lieutenant Capron 
has the difficult post of instructor of sergeants at Fort 
Whipple. 
Where a single person has been required to do the work 
of a station, receiving full reports from all stations, the 
labour occupied twenty hours out of the twenty-four. But 
the rule now adopted is to provide each station with two 
men—one a sergeant in charge and the other a private 
soldier as assistant. The observer stationed on Mount 
Washington has been alone on the mountain most of the 
time, and always responsible for the work. 
In addition to a number of officers who form the 
Board of Examination, General Myer is also ably assisted 
by Major L. B. Norton, the property and disbursing officer 
of the Signal Service. 
Prof, Cleveland Abbé, long known as an officer of the 
Cincinnati Observatory, and as an eminent meteorologist, 
is employed chiefly in the work of making out the daily 
synopsis of the weather, and deducing therefrom the 
weather “ probabilities,” which are given to the public by 
telegram through all newspapers desirous of furnishing 
them to their readers, 
To the conspicuous ability of all of these officers is 
attributable the success of the enterprise. 
The ordinary barometer in use by Signal Office ob- 
servers is that of Mr. James Green (the well-known scien- 
tific instrument maker of New York)—an instrument 
adopted by the Smithsonian Institution, and also by the 
American navy, as the most perfect to be obtained. 
This barometer has its cistern furnished with a small 
glass index, which shows when the mercury is at the right 
height in the cistern. This is adjustable by a screw which 
works through the bottom of the instrument against the 
flexible bottom of the cistern. The instrument is ready 
for use when the mercury touches the little V-shaped 
index in the cistern. So simple and complete is this 
barometer that any one can use it, and it ought to be in 
the hands of all business gentlemen, and all who are inte- 
rested in watching the mutations of the weather. 
Latitude and longitude on the earth’s surface mark very 
conspicuous differences in the mean barometrie pressure, 
as will be seen by a study of the Isobarometric Chart for 
the United States, which we gave last week. 
The barometer has a slight fluctuation also under 
several influences. It rises when the moon is on the 
meridian in some places. It has a diurnal oscillation, 
amounting on the equator to more than one-tenth of an 
inch, but in the latitude of New York to only o’05 inch, 
the greatest height being about ten a.M., and the least 
about four P.M. The nocturnal variations are much less. 
In the latitude of Philadelphia and New York the north- 
east wind causes another variation of one-fourth of an 
inch, due to the meeting of two atmospheric waves giving 
a still higher wave, and hencea higher barometer. There 
