Jf. REPORT—1874. 
tongs pressure on the square inch, The manner of protecting the bulb was invented 
by Messrs. Negretti and Zambra in 1857 (at which time a number were made for 
the late Admiral FitzRoy), and has been lately copied and 
brought out as a new invention by other persons. 
The construction of the instrument for deep-sea temperatures 
is as follows :— 
In shape it is like a siphon with parallel legs, all in one 
piece and in continuous communication. The scale of the 
thermometer is pivoted on a centre, and being attached in a 
perpendicular position to a simple apparatus, is lowered to any 
depth that may be desired. its descent the thermometer 
acts as an ordinary instrument, the mercury rising or falling 
according to the temperature of the stratum through which it 
passes; but so soon as the descent ceases, and a reverse motion 
is given to the line, so as to pull the thermometer towards the 
surface, the instrument turns once on its centre, first bulb 
uppermost, and afterwards bulb downwards. ‘This causes the 
mercury, which was in the left-hand column, first to pass into 
the dilated siphon bend at the top, and thence into the right- 
hand tube, where it remains, indicating on a graduated scale 
the exact temperature at the time it was turned over. The 
woodcut shows the position of the mercury after the instru- 
ment has been thus turned on its centre. A is the bulb; B the 
outer coating or protected cylinder; C is the space of rarefied 
air, which is reduced if the outer casing be compressed ; D is a 
small glass plug on the principle of Negretti and Zambra’s 
Maximum Thermometer, which cuts off, in the moment of 
turning, the mercury in the tube from that of the bulb, thereby 
ensuring that none but the mercury in the tube can be trans- 
ferred into the indicating column; E is an enlargement made 
in the bend so as to enable the mercury to pass quickly from 
one tube to another in revolving; and F is the indicating tube 
or thermometer proper. In its action, as soon as the thermo- 
meter is put in motion, and immediately the tube has acquired 
a slightly oblique position, the mercury breaks off at the 
point D, runs into the curved and enlarged portion KE, and 
eventually falls into the tube F when this tube resumes its 
original perpendicular position. 
The contrivance for turning the thermometer over in the sea, 
either at the bottom or at any depth which may be desired, 
may be described as a vertical propeller to which the thermo- 
meter is pivoted; this is fixed to a line, and as long as the 
apparatus is descending the propeller remains still; but as soon 
as the line is pulled up and the ascent commences, it begins to 
revolve and continues to do so until the thermometer is turned 
over (which it does in less than two fathoms), and then 
remains fixed and immovable. 
For atmospheric purposes and observatories the thermometer 
is turned over by means of a simple clockwork; two thermo- 
meters fitted as hygrometers can be turned over as easily as 
one; and it is suggested that this instrument might supersede 
the large, cumbersome, and expensive thermographs at present 
in use. 
LONDON 
& ZAMBRA 
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A Four-Pendulum Apparatus. By 8. C. Trstry. 
At the Bradford Meeting the author described a two-pendulum apparatus for 
drawing rectangular harmonic curves. In the construction of that apparatus two 
defects were present—each vibrator working on the other as a centre, the tracer 
described portions of two circular ares; but when each was vibrated separately, 
