1817.} Description of a new portable Barometer, 313 
then dressed, and healed in about a month. ‘The animal was after- 
wards turned into some grass pasture, and appears going on well. 
Simple puncture does not answer; for unless the cyst is removed, 
the water accumulates again. 
 P.S. Your correspondent S. appears to have mistaken my ideas 
with regard to the thermometer scale. If he re-peruses that article, 
he will find that I said Fahrenheit’s scale was arbitrary, and recom 
‘mended the decimal scale beginning with zero. 
a anne 
ArTICcLE VI. 
A Description of a new portable Barometer and a new Hygrometer: 
By Daniel Wilson, Esq. 
Tue high degree of perfection which physical science has 
attained is in a great measure to be ascribed to the excellence of 
our philosophical instruments. Until experimental investigation 
was assisted by the thermometer, barometer, and air-pump, few or: 
no important natural facts were ascertained, or general laws of 
matter established; whilst every subsequent discovery of an addi- 
tional agent has opened a new field of scientific inquiry. 
Within these few years, since the study of geology has become 
more general, and that the observations of men of science have 
been directed to the investigation of the influence of elevation on 
vegetation and meteorology, much attention has been bestowed on 
rendering the barometer portable, and on simplifying its application 
to the mensuration of heights. The labours of Ramsden, Deluc, 
General Roy, Sir George Shuckburgh, Dr. Hamilton, Dr. Maske- 
yne, Professor Leslie, Professor Playfair, Dr. Macculloch, M. 
Fortin, and M. Biot, have been at various times successfully en- 
gaged in promoting these objects; and more particularly by Sir 
Henry Englefield and M. Gay-Lussac, the common barometer has 
been brought to as great a degree of perfection with regard to 
portability as its principle seems to admit of. But from the length 
of the mercurial column required to balance the weight of the 
atmosphere, it must always be an inconvenient instrument to the 
traveller; especially since it is oftenest used in ascending those more 
inaccessible regions where a trifling weight becomes a burden of 
magnitude. 
It is perhaps for this reason that barometrical observations, in their 
application to the admeasurement of heights, have not yet become 
so general as their importance merits, 
By constructing a uew barometer on just principles, possessing 
at the same time accuracy and portability, I cannot but hope that 
some facilities will be given to the prosecution of this department of 
science, and that in a short time it will be enabled to keep pace 
with the gencral progress of discovery, 
