408 
POPULAE SCIENCE EEVIEW. 
wich timCj resting on the table^ but hanging to a hook in the 
framework. The next instrument on the framework was a 
Eegnault^s hygrometer with a single silver cup (10)^ with a tube 
leading from it with a glass terminal of sufficient length_, that 
when blowing into it by the mouthy any other instrum ent^ at any 
part of the table_, could be read. Next to this instrument was 
the mercurial barometer^ a perforation being made in the table 
admitting its lower branch to descend below (11), leaving the 
upper branch (12) at a convenient height for observing^ with 
respect to the other instruments. Near to this instrument was 
placed a large aneroid barometer (13)^ its lower part resting 
on the table, while its upper part was fixed to the framework ; 
above this instrument, placed on the framework, was a second 
Regnaulks hygrometer (14) with a pair of gold cups ; in the 
lower part of its central supporting stem there was an open 
projecting pipe, with flexible tube attached, leading to the 
aspirator below. A DanieTs hygrometer (15) occupies the 
next position, conveniently placed for inversion with the right 
hand, and admitting a ready perception of the first appearance 
of dew, being nearly central among the instruments ; beyond 
these are placed two exceedingly delicate thermometers, the 
one with a spiral bulb (16), and the other with a gridiron form 
of bulb (1 7) j beneath these, resting on the table, are two 
spectroscopes (18 and 19), and at the extreme right hand (20) 
HerscheTs actinometer ; on the table, besides, is a lens with 
bottles of water and aether. Beneath the table the aspirator 
(21) was fixed, near the centre of the table, so as to be 
conveniently worked by the hands, by taking hold of 
both sides, or by the foot resting on the trestle beneath. 
Holes were cut in the board to admit the passage of the 
flexible tube from the dry- and wet-bulb thermometers and the 
flexible tube from BegnaulBs hygrometer, previously referred 
to, both of these tubes being furnished with stop-cocks (22 
and 23). 
Whilst this operation was proceeding, the readings of other 
instruments were taken and recorded till the time approached 
when undivided attention was required to the right-hand gold 
cup of instrument' 14, in comparison with its left-hand gold 
cup, to note the first dimming of the bright surface of the former 
by the deposition of moisture upon it, then to cease working 
the aspirator to read both the instruments of 14 and then to 
read instruments 7 and 8» 
The mercurial barometer employed was a Gay-Lussac^s 
siphon. The inner diameter of its tube is J of an inch. 
The graduations were made on a brass scale from its middle 
point upwards and downwards ; each division was about 0’05 
inch in length, representing twice that value ; so that an 
