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ON SELF-REGISTERING METEOROLOGICAL INSTRUMENTS. 109 
Meteorological Observations made at Prague; it is therefore deemed suffi- 
cient now only to state that they register from five to five minutes the va- 
riations of pressure, temperature and moisture of the atmosphere. The 
appended numerical Tables contain the hourly variations, and are of course 
only extracts made from the original curves marked from five to five minutes 
by the autograph, which was deemed sufficient for ascertaining the numerical 
value of any point of the curve. The series now submitted to observation 
is selected from and confined to days when considerable atmospheric changes 
occurred, so as to afford a proof of the advantage to be derived by em- 
ploying such instruments. On other days, where the variations are more 
confined to the ordinary rates, fewer observations and at greater intervals are 
sufficient to make these apparent, us on such days the differences in variation 
at less distant places are so insignificant that they become scarcely percepti- 
ble; no doubt however the medium of extended regular observations would 
afford the means to appreciate such, but for the present and first attempt and 
trial, days when the atmosphere was more agitated seem better suited for 
the proposed purpose. [Table II. contains the Observations for the 18—-19th 
June as an example. ] 
The two stations where these observations were made are,—1. Senftenberg, 
which is nearly due east 100 English miles from Prague, a distance quite 
sufficient to produce variations in these phenomena, which are however in- 
creased by other local causes. The observatory there is situated on the 
centre of the property on the river Adler, 1281 Paris feet above the level of 
the sea, in latitude 50° 5! 8!'-8, and longitude, east of Greenwich, 1" 5! 46!"-98. 
Its immediate site is on lias and mica slate, but at no great distance it is more 
or less surrounded by higher ground with granite, gneiss and old red sand- 
stone, and considerable forests. 2. Prague, situated in a more level country, 
and the river Moldau flowing through the town with a breadth of about 200 
fathoms, is only 524 Paris feet above the level of the sea, without much 
woodland in its neighbourhood, the lower strata of the surrounding hills 
being principally lias, sandstone and argillaceous schist,—all circumstances 
which may produce influence on the atmospheric variations. 
After these preliminary remarks, a little attehtion to the curves described 
by both barometrographs will soon convince us that they run nearly parallel, 
and that it is more particularly the deviation from parallelism which should 
be more nearly examined. The pressure of the air at Prague being 0°9 
inch greater than at Senftenberg, and the curve of Prague being the lower 
one, their approach towards each other when the curves are rising proves 
that the rising commenced earlier at Prague than at Senftenberg ; whereas 
an approach when the curves are descending denotes a quicker diminution 
of the pressure at Senftenberg. This is applicable to the extreme bends, or 
those points of the curve where a maximum in either sense has taken place, 
where the rising passes into falling, or the reverse ; and in those cases when 
a curye that was before running nearly in a horizontal direction gradually 
begins to rise or fall; but if two curves continue for a while both to rise or 
to fall, a gradual convergency or divergency must also be accounted for by 
the weight of the atmosphere undergoing a change of the same nature at 
both places, but a greater one in the one than the other. Variations, how- 
ever, observed during a longer period, embracing a succession of days, are 
generally so nearly of the same value at both stations, that by present expe- 
rience no decided opinion can be expressed in which of them the total 
_ amount of change is greatest. 
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e annexed Table shows the amount of barometric variation during forty- 
five days, by which it appears that the medium at Prague was only 0°005 inch 
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