348 PHYSICS. 



have the upper extremity of the tube turned into a ring with its plane 

 parallel to the enameling* in the tube. It is desirable further to have 

 the kind of glass and the date of filling engraved on the tube. {Nature, 

 June, 1881, xxiv, 100.) 



Marey has contrived a new continuous registering thermometer for 

 recording the temperature of the bodj'. It consists of a closed brass 

 tube containing oil and communicating with a Bourdon manometer. 

 Any change of temperature by altering the internal pressure makes the 

 curve of the manometer increase or decrease, thus registering the change 

 by means of an index on a revolving cylinder. The tliermometric bulb 

 may be at a distance from the recording apparatus, the two being con- 

 nected by a tube of annealed copper. Two such bulbs may be employed 

 and applied to dilierent parts of the body, exterior or interior. {Nature, 

 July 28, 1881, xxiv, 294.) 



Brown has devised a modification of the mercurial thermometer by 

 which temperatures may be electrically registered at a distance. It 

 was invented for the purpose of ascertaining the temperature of kilns 

 for drying malt, and works well in i3ractice. An ordinary thermometer 

 9 inches long with a large bulb and wide stem has platinum wires in- 

 serted through the walls of the stem every three degrees from 120° to 

 171° v., their outer ends being connected with binding screws. The bore 

 of the tube above the mercury contains glycerin. Another wire of pla- 

 tinum passes through the bulb and communicates with the mercury. Its 

 outer end is attached to a binding post by which connection is made 

 with one pole of a Leclanche battery of two cells, the other pole being- 

 grounded. Near the thermometer is placed a transmitter consisting of 

 an ebonite ring through which platinum wires pass at equal distances, 

 their upper ends flush with the surface. An arm revolving by clock- 

 work, and started by an electro-magnet, touches each of these wires in 

 succession. As they are severally connected with the thermometer wires 

 the circuit is closed by those wires with which the mercury is in con- 

 tact, and a signal is sent down the line, with which the moving arm is 

 connected, and which may be of any length. By closing the cii-cuit of 

 a second line wire, the electro-magnet starts the clock-work, and the 

 traversing arm completes the circuit through a bell as many times as 

 there are Avires immersed in the mercury. This number multiplied by 

 three and the sum added to 120° gives the temperature. {Nature, 

 March, 1881, xxiii, 464.) 



Langley has given the following calcidation: A sunbeam one square 

 centimeter in section is found in the clear sky of the Allegheny Mount- 

 ains to bring to the earth in one minute enough heat to warm one gram 

 of water by 1° C. It would, therefore, if concentrated upon a film of 

 water one five-hundredth of a millimeter thick, one millimeter wide, 

 and ten millimeters long, raise it 83i^o in one second, provided all the 

 heat could be maintained. And since the specific heat of platinum is 



