GLEANINGS 
IN 
SCIENCE. 
No. 11. — November, 1829. 
T.—On the most eligible Form for the. Construction of a Portable 
Barometer. With a Plate. 
It has hcen often made a subject of regret amongst those who take an interest in 
the enquiries of the metereologist, that there is no popular and full account of an 
instrument in such general use as the barometer. Were such a task well executed, 
and the different forms of the instrument, as usually made for sale, accurately de- 
scribed ; their respective advantages and disadvantages clearly stated and compared 
with their prices ; there is little doubt but it would be found highly useful. J o the 
person desiring to possess a barometer, and wishing that it should be capable of an- 
swering the purpose for which he requires it, it is surely of importance to be made 
acquainted with all the peculiarities of the instrument, and of the modifications 
which may be induced by any particular method of constructing it. It is not un- 
common to see a person, for want of this information, burden himself with an expen- 
sive instrument, which proves, when it comes to be used, totally unserviceable ; while 
all are misled so far as to think a perfectly accurate barometer may not be had for 
about one third of the sum generally paid, or even less. 
In the absence of such a work, I propose to give, what perhaps may not be with- 
out its use a description of a barometer which I haveemployedforthe lastfive years, 
and which' has fully answered my expectations. I consider its advantages to be, 
greater portability, less liability to accidents, and greater economy in the first cost ; 
while no difficulty is found to attend the applying new tubes, when in the course of 
time the old are broken. Excepting in some instruments constnicted by Berge, this 
operation is not easily performed ; so that when once the tube of one of these expen. 
sive instruments is broken, there is no repairing it without sending it to England. 
This is a serious objection. , , 
A barometer is by many supposed to be a very mysterious and complicated ma- 
chine ; whereas, in theory nothing can be simpler : and the nearer this simplicity is 
adhered to in practice, the more useful is the barometer likely to be. After all the 
talent and mechanical contrivance that has been brought to bear on the subject, I 
am inclined to think the old and simple arrangement of the tube standing in an open 
vessel of mercury, is not only the best in every other point of view but also the most 
portable. Or if I were to allow of any possible improvement on it, it would be the 
form generally used on the continent, where they give the tube the syphon shape, and 
by that means dispense with the cistern. The former arrangement I have now used 
for five years, during which period 1 have constantly been on the i move; and I can give 
my testimony to its superior portability, durability, accuracy, ami above all, economy. 
Those commonly called Englefield's portable barometers are, as every one who 
has used them knows, subject to derangement by the leakage of the mercury from 
the wooden cistern. This, it is true, when the evil goes no further, may be corrected 
by comparing them with a standard ; but as a person travelling cannot carry with 
him or have access on every occasion to a standard of comparison, and as the 
leakage is stiU liable to occur at any time, observations made with such a baro- 
