852 2'jiAu\S ACTIO AS OF THE AMERICAN INSTITUTE. 



will have motion, and travel in a circle, but, when a knife or other 

 article is placed in the water, the motion of the particles of camphor- 

 will stop. 



The Chairman alluded to the theory of motion of Prof. H. F. 

 Walling, a member of the association, and published in our Trans- 

 actions for 1866-7, in which a molecular theory is fully and ably set 

 forth. 



Temperature in Deep Water. 



Dr. Vanderweyde remarked that he liad invented a pyrometer on 

 a principle nearly the same as that mentioned in the item just read 

 by the Chairman. A tubular metallic stem inclosed a rod of another 

 metal, and had at one end a bulb to contain a ratchet wheel and 

 pointer. The greater expansion of the rod caused a pawl to turn 

 the pointer to indicate the degree of heat. The apparatus was not 

 approved on trial, because, after being subjected to a high heat, the 

 parts failed to resume their original position, the instrument being 

 thus rendered worthless. A lower temperature of the air will con- 

 duct more electricity than if the temperature is higher. To test the 

 temperature of deep water, a galvanic battery and a galvanometer 

 are the best instruments to use. 



Prof. Phin referred to the well known Brequet thermometer, 

 composed of annular or curved strips of metal riveted together 

 in such a way that the difference of expansion in the two strips, by 

 varying the curvature of the device, indicates the degree of change 

 in the temperature. 



The Chairman remarked that this thermometer was found not 

 reliable in practice ; but a device having two straight rods or plates 

 of metal might be made to answer the purpose, appliances being 

 used to obviate interference from increased pressure of the water at 

 great depths, and also to register the change of temperature as indi- 

 cated by the difference of expansion of the two parts; but all ther- 

 mometers made of solid metal undergo certain changes, so that their 

 graduation must be readjusted from time to time. 



Dr. J. F. Boynton stated that about fifteen years ago he devised an 

 apparatus for this purpose. It was composed of an acorn-shaped 

 Bhell, provided with a pressure gauge recording up to 600 pounds per 

 square inch, and designed to register the pressure at the depth of the 

 Bounding. This gauge was connected with mechanism inclosed 

 within the shell, to which an electic wire was attaclied extending to 

 the surface; this wire beino; so arranged in relation with tlie ratchet- 



