A Treatise on Meteorological Instruments Part 21

L. F. KaeMTZ'S "COMPLETE COURSE OF METEOROLOGY,"

Translated by C. V. WALKER, Esq.

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PRACTICAL METEOROLOGY, By JOHN DREW, Ph.D., F.R.A.S.

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HYGROMETRICAL TABLES, Adapted to the use of the Wet and Dry Bulb Thermometer, By JAMES GLAISHER, Esq., F.R.S.

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TABLES OF THE CORRECTIONS FOR TEMPERATURES, To reduce observations to the 32 Fahrenheit, for Barometers with bra.s.s scales extending from the cistern to the top of the mercurial column, By JAMES GLAISHER, Esq., F.R.S.

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TABLE OF THE DIURNAL RANGE OF THE BAROMETER, By JAMES GLAISHER, Esq., F.R.S.

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TABLES FOR CALCULATION OF HEIGHTS FROM OBSERVATIONS ON THE BOILING-POINT OF WATER, Adapted to the use of Negretti and Zambra's Boiling-point Apparatus.

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A THERMOMETRICAL TABLE, ON THE SCALES OF FAHRENHEIT, REAUMUR, AND CENTIGRADE, By ALFRED S. TAYLOR, Esq., M.D., &c.

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METEOROLOGICAL TABLES, For the reduction of Barometrical and Hygrometrical Observations, Determination of Heights by the Barometer and Boiling-point Thermometer, &c.

By G. HARVEY SIMMONDS, M.B.M.S.

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BAROMETER MANUAL, Compiled by Vice-Admiral FITZROY, F.R.S., For the Board of Trade.

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POCKET METEOROLOGICAL REGISTER AND NOTE-BOOK, With Diagrams for exhibiting the Fluctuations of Barometer, &c.

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LONDON: PRINTED BY STRAHAN AND WILLIAMS, 7 LAWRENCE LAND, CHEAPSIDE, E.C.

NEGRETTI & ZAMBRA'S

PATENT RECORDING AND DEEP-SEA THERMOMETER.[20]

This Thermometer differs from all other Registering or Recording Thermometers in the following important particulars:--

I. The Thermometer contains only Mercury without any admixture of Alcohol or other fluid.

II. It has no indices or springs, and its indications are by the column of Mercury only.

III. It can be carried in any position, and cannot possibly be put out of order except by actual breakage of the instrument.

And lastly, it will indicate and record the exact temperature at any hour of the day or night, or the exact temperature at any depth of the sea, irrespective of either warm or cold currents, or stratum through which the Thermometer may have to pa.s.s in its descent or ascent, this last very special quality renders this Thermometer superior for deep-sea temperatures to any others; for those now being used in the "Challenger"

sounding expedition are liable to give erroneous indications owing to their indices slipping, and otherwise getting deranged--(This was proved by Messrs. Negretti and Zambra at a Meeting of the British Meteorological Society,) and _under certain conditions of temperature_ it is not possible by the old Thermometers to obtain true temperatures at certain depths which might be required. _Annexed is a copy of a report to the Admiralty from Captain G. S. Nares, of H.M.S. "Challenger," dated Melbourne, March 25th, 1874, which we have taken from NATURE, July 30th, 1874, proving the a.s.sertion._

"In the report to the Admiralty of Capt. G. S. Nares, of H.M.S.

_Challenger_ dated Melbourne, March 25, 1874, Capt. Nares, speaking of the temperature of the ocean, especially near the pack edge of the ice, says:--'At a short distance from the pack, the surface water rose to 32, but at a depth of 40 fathoms we always found the temperature to be 29; this continued to 300 fathoms, the depth in which most of the icebergs float, after which there is a stratum of slightly warmer water of 33 or 34. As the thermometers had to pa.s.s through these two belts of water before reaching the bottom, the indices registered those temperatures, and it was impossible to obtain the exact temperature of the bottom whilst near the ice, but the observations made in lower lat.i.tudes show that it is about 31. More exact results could not have been obtained even had Mr.

Siemens's apparatus been on board.' It seems to us that the difficulty mentioned is one which would certainly have been surmounted by Messrs.

Negretti and Zambra's new Recording Thermometers, a description of which appeared in NATURE, vol. ix. p. 387; this being exactly one of the cases to which this instrument is peculiarly adapted. We believe the inventors and makers have greatly improved their Thermometer since our description appeared, and no doubt means will be taken by the Admiralty to transmit one to the _Challenger_."

DESCRIPTION OF THE DEEP-SEA RECORDING THERMOMETER.

In the first place, it must be observed that the bulb of the Thermometer is protected so as to resist the pressure of the ocean, which varies according to depth that of three thousand fathoms being something like three tons pressure on the square inch. The manner of protecting the bulb was invented by Messrs. Negretti and Zambra in 1857, and has been latterly copied by other persons and brought out as a new invention. The manner of protecting the bulb has been described by the late Admiral R. FitzRoy, in the first number of Meteorological Papers, page 55, published July 5th, 1857, as follows:

"Referring to the erroneous readings of all thermometers, consequent on their delicate bulbs being compressed by the great pressure of the ocean, he says:--'With a view to obviate this failing, Messrs.

Negretti and Zambra undertook to make a case for the weak bulbs, which should transmit temperature, but resist pressure. Accordingly a tube of thick gla.s.s is sealed outside the delicate bulb, between which and the casing is a s.p.a.ce all round, which is nearly filled with mercury.

The small s.p.a.ce not so filled is a vacuum, into which the mercury can be expanded, or forced by heat or mechanical compression, without doing injury to or even compressing the inner or much more delicate bulb.'"

[Ill.u.s.tration: Fig. 1.]

The construction of this instrument for deep-sea temperatures is as follows:--

In shape it is like a syphon with parallel legs, all in one piece and having a continuous communication, as in the annexed figure. The scale of the Thermometer is pivoted on a centre and being attached in a perpendicular position to a simple apparatus (which will be presently described), is lowered to any depth that may be desired. In its descent the Thermometer acts as an ordinary instrument, the mercury rising or falling according to the temperature of the stratum through which it pa.s.ses; 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 pa.s.s into the dilated syphon 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, Fig. 1, shows the position of the mercury _after_ the instrument has been thus turned on its centre.

A is the bulb; B the outer coating or protecting cylinder; C is the s.p.a.ce of rarefied air, which is reduced if the outer casing be compressed; D is a small gla.s.s plug on the principle of Negretti and Zambra's Patent 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 transferred into the indicating column; E is an enlargement made in the bend so as to enable the mercury to pa.s.s quickly from one tube to another in revolving; and F is the indicating tube or Thermometer proper. In its action, as soon as the Thermometer 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 E, and eventually falls into the tube F when this tube resumes its original perpendicular position.

The contrivance for turning the Thermometer over may be described as a frame with a vertical propeller; to this frame the instrument is pivoted.

On its descent through the water the propeller is lifted out of gear and revolves freely on its axis; but so soon as the instrument is pulled towards the surface the propeller falls into gear and revolves in the contrary direction, turning the Thermometer over once, and then becoming locked and immovable.

_Directions for adjusting the Thermometer previous to its being lowered in the Sea._

I. The mercury must all be in the left-hand column.

II. The short peg at the back of the thermometer must be in front of the stop plate S +; in order to effect this, pull the k.n.o.b which stops the Thermometer, and slightly turn the propeller, to make the Thermometer advance sufficiently to escape the stop plate.

Negretti & Zambra's Patent Atmospheric Recording Thermometer, Fig. 3, differs from the Deep-sea Thermometer by its not having the double or protected bulb, it not being required for resisting pressures. In this case the instrument is turned over by a simple clock movement, which can be set to any hour it may be desirable; the Thermometer is fixed on the clock, and when the hand arrives at the hour determined upon, and to which the clock is set as in setting an alarum clock, a spring is released and the Thermometer turns over as before described.

[Ill.u.s.tration: Fig. 2.]

[Ill.u.s.tration: Fig. 3.]

Messrs. Negretti and Zambra have arranged a Wet and Dry Bulb Hygrometer upon the same plan.