DOI Seite / Zitierlink:
https://doi.org/10.11588/diglit.20140#0052
28
thermometers and graphical representations.
and scale, and is very well adapted for standards which always are used with every
possible care; but for general purposes they are not solid enough, and, which is more
important perhaps, in all cases in which the bulb and the stem cannot be absolutely
of the same temperature (as in determining the temperature of the surface of the
ground, of springs, &o), a sensible error can be produced by the bulb being of a
different temperature from that of the stem, whilst in the thermometers we generally
used the second cylinder surrounding the stem is a decided protection.
The thermometers of the Indian Medical Establishment I found to be, with
few exceptions, by the best makers in England, such as Adie, Elliot, Newman,
Troughton, Simons, &c.; and, as thermometers have so much less to risk by being
sent about than other instruments, viz. barometers, &c, they were generally in perfect
order.
Our own thermometers I had made at Berlin (whilst Adolphe was then occupied
with other preparations in London), partly by Geissler, partly by Gtreiner. They
differed from those of English construction in as much as the scale was not placed
upon the glass stem, or, as is more general, upon metallic plates, but upon
semi-transparent glass, enclosed together with the capillary tube in a cylinder of
glass. The bulb naturally remained uncovered by this cylinder, which was attached
immediately above it; in Germany for ordinary purposes also a paper scale is
enclosed instead of the scale of transparent glass. This form considerably reduces
the secondary influence of the temperature of the scale. They were all kindly
compared at the Kew Observatory by Mr. Welsh, before our departure, and the
freezing and boiling points were also frequently controlled during our travels.
In consequence of the contraction of the bulb of the thermometer not yet reach-
ing its maximum with the cooling of the glass, it generally happens that the scale
of the thermometers, notwithstanding its partial and local irregularities, is a little
too high throughout; this correction can best be determined at the freezing point; I
had occasion in many instances to fix it also for the stations by direct comparison
with our standard thermometers from Kew. It generally exceeded Fahr., not
unfrequently it reached 1 ° Fahr. The means given in the following tables of this
volume are already corrected; in the means formerly published in the Journal As.
Soc. I found such corrections constantly neglected wherever I had occasion to trace
them to the original manuscripts.
thermometers and graphical representations.
and scale, and is very well adapted for standards which always are used with every
possible care; but for general purposes they are not solid enough, and, which is more
important perhaps, in all cases in which the bulb and the stem cannot be absolutely
of the same temperature (as in determining the temperature of the surface of the
ground, of springs, &o), a sensible error can be produced by the bulb being of a
different temperature from that of the stem, whilst in the thermometers we generally
used the second cylinder surrounding the stem is a decided protection.
The thermometers of the Indian Medical Establishment I found to be, with
few exceptions, by the best makers in England, such as Adie, Elliot, Newman,
Troughton, Simons, &c.; and, as thermometers have so much less to risk by being
sent about than other instruments, viz. barometers, &c, they were generally in perfect
order.
Our own thermometers I had made at Berlin (whilst Adolphe was then occupied
with other preparations in London), partly by Geissler, partly by Gtreiner. They
differed from those of English construction in as much as the scale was not placed
upon the glass stem, or, as is more general, upon metallic plates, but upon
semi-transparent glass, enclosed together with the capillary tube in a cylinder of
glass. The bulb naturally remained uncovered by this cylinder, which was attached
immediately above it; in Germany for ordinary purposes also a paper scale is
enclosed instead of the scale of transparent glass. This form considerably reduces
the secondary influence of the temperature of the scale. They were all kindly
compared at the Kew Observatory by Mr. Welsh, before our departure, and the
freezing and boiling points were also frequently controlled during our travels.
In consequence of the contraction of the bulb of the thermometer not yet reach-
ing its maximum with the cooling of the glass, it generally happens that the scale
of the thermometers, notwithstanding its partial and local irregularities, is a little
too high throughout; this correction can best be determined at the freezing point; I
had occasion in many instances to fix it also for the stations by direct comparison
with our standard thermometers from Kew. It generally exceeded Fahr., not
unfrequently it reached 1 ° Fahr. The means given in the following tables of this
volume are already corrected; in the means formerly published in the Journal As.
Soc. I found such corrections constantly neglected wherever I had occasion to trace
them to the original manuscripts.