12 REPORT 1867. 



long periods. I liave therefore de-\-ised a new class of telegraphic meteorometers 

 wliich shall be independent of clockwork, and may remain in any situation of diffi- 

 cult access as long as the instrument endures. This principle is applicable to all in- 

 struments which indicate by means of a revolving hand, and I have already devised 

 its application to a Breguet's metallic thermometer, an aneroid barometer, and an 

 hygrometer, depending on the absorption of moisture by a thin membrane. It is also 

 applicable to a bar-magnet in a fixed position, and to a variety of other indicators. 



The apparatus consists of two distinct instruments, connected only by telegraphic 

 wires : the first I will call the questioner (A) ; the second, the responder (B). 



The questioner (A) is a rectangular box presenting externally a circular dial face, 

 round which are engraved the degrees both of the Fahrenheit and Centigrade ther- 

 mometric scales : the former ranging from 20° below zero F. to 220° above that 

 point, and the latter from 0"" to 110° C. It shows besides three binding screws for 

 the pm-pose of connecting the telegraphic wires, and a handle which causes the 

 rotation of the armature of a magnetomotor in the interior. This magnetomotor 

 is similar in its construction to that emjiloj-ed in my alphabetic magnetic tele- 

 graph ; a soft iron armatui-e rotating before the four poles of the magnet occasions, 

 when the circuit is completed, alternate currents of equal intensity. The box also 

 contains a small electromagnet which acts bv means of mechanism similar to that 

 employed in the indicator of the aforesaid telegraph, and causes the revolution of 

 the index of the dial. 



The responder (B) is a cylindi-ical brass box which presents on its upper surface 

 a similar dial with its thermometric scales and index ; at its base three binding 

 screws, corresponding to those of the questioner, are fixed for connecting the tele- 

 gi-aphic wires, and it is furnished with a brass cover that it may be hermetically 

 sealed when lowered in the sea or bm-ied in the ground. Its interior contains three 

 essentially distinct parts : — 1. The metallic thermometer, which consists of a spiral 

 ribbon of two dissimilar metals, with its hand capable of ranging through the ex- 

 tent of the circvdar thermometric scale of the dial. 2. A small electromagnet, 

 acting by means of a propelment on a disk, making as many stops in one rotation as 

 there are half degrees on the scale. .3. An axis, to which is fixed a delicate spiral 

 spring which causes a pin to bear lightly against the hand of the thermometer, 

 however it may vary in position. 



The two iusti'umeuts are connected by means of two telegraphic wires. The 

 first proceeds from an earth-plate at the near station, passes through the coil of the 

 electromotor in A, joins the coil of tlie small electromagnet in B, and then pro- 

 ceeds to another eai'th-plate at the distant station. The second wire is perma- 

 nently connected with the first between the earth-plato and the coil of the mag- 

 netomotor, and includes that of the electromagnet in B, and its opposite end is 

 brought close to the remote end of the first wire. The mechanism is so disposed 

 that when the first wire is disconnected from its earth terminal it is brought into 

 circuit with the second wire. 



By this arrangement, when the dial of A is brought to 0° and the handle turned, 

 at the first moment the ch-ciut is completed through the first wire, containing the 

 coil of the electromagnet in B, and the return earth. .\ disk is thereby caused to 

 revolve in an opposite direction to the gi-aduation of the scale, until a pin, originally 

 starting from O'", comes into contact with t!ie pin pressing against the thennometer 

 hand, and thereby comjiletes the circuit of the second wire and breaks the connexion 

 with the earth-plate. At first only the electromagnet in B is acted upon, but 

 when the cun-ents are diverted into the new channel, both the electromagnets 

 act simultaneously. In consequence of the action of the electromagnet, in A the 

 hand of its dial passes over a space corresponding witli that between 0° and that 

 indicated by the thermometer, and the hand of the dial ultimately accords with 

 that of the distant thermonicter. When the hand of tlie dial on A comes to rest, 

 the di.sk in B arrives at 0°, and a catch permits the spiral spring to unwind itself, 

 and its pin fiies to and presses against the thermometer hand. 



It must be observed tliat instruments thus constructed are not capable of mark- 

 ing every possible gradation ; but they may be made to indicate divisions of the 

 scale of any reqiured minuteness. It is ad^-isable to limit the extent of the scale 

 when more minute divisions are deemed necessary, 



