44. G. W. Hough on an Automatic printing Barometer. 
The only method by which this has been hitherto attempted 
with success has been by the application of photography. is, 
though a very considerable advance, and probably all that could 
be desired in respect of continuity and accuracy of the record, is 
liable perhaps to the objection that it is too complicated a pro- 
cess for general use. If we consider the skill requisite in the 
preparation of the paper, the delicacy of manipulation involved 
by the apparatus, and the labor of interpreting the results, as 
compared with the average capacity and means of the great 
number of observers desired and likely to volunteer or be em- 
loyed for such a purpose, it would seem that a simpler process 
is both desirable and necessary. This it has been my intention 
to furnish, and with what success remains for time and experi- 
ence to determine. The importance of the subject will justify 
me perhaps in presenting some account of the new method. 
The problem to be solved, was to cause any meteorological in- 
strument, by means of suitable mechanism, simply and effectually 
to record its own changes. The instrument selected for experi- 
ment was the barometer. When any delicate instrument is 
made to record its own changes by mechanical means, the chief 
difficulty is that of getting sufficient power for the mechanism 
attached to make a distinct and continuous record, without tak- 
ing a perceptible amount of force from the instrument itself, and 
thereby vitiating the results. The use of electricity naturally 
suggested itself as the best means of overcoming this obstacle. 
This agency has not as yet been made economical or certain as 4 
motor, but is chiefly valuable in controlling power obtained 
through some other means. By it, as may be seen in its appli- 
cation to clock work, and in the telegraph, the movements of one 
machine may be reproduced in an other with no greater expen- 
diture of force than is requisite for electrical contact. In the — 
cases cited, however, the motion to be reproduced is sensibly 
uniform and in the same direction. For the solution of our 
problem, a mechanism is demanded that shall repeat the changes — 
of the original in every form, whether the motion be uniform or — 
variable, forward or reverse. a 
The feasibility of this plan was discussed with my friend Mr. — 
homas Simons as early as the year 1862, and some steps were — 
then taken to apply it to the thermometer. J may here express — 
my acknowledgments to Mr. Simons for valuable suggestions in — 
the construction of the present machine. Various plans were 
considered for effecting the electrical contact with the fluctuating — 
medium which is the basis of this method. It was at first pro- 
posed to do this at the surface of the mercury in a siphon ba- 
rometer, by means of a platinum wire which should be carried 
continually toward the mercury surface by suitable mechani 
and on touching the surface, a galvanic current would be fc 
