BRITISH ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE. 53 

 aEPORT ON THE DEVELOPMENT OF HEAT IN AGITATED WATER. — BT ME. G. EENNIE. 



Mr. Kennie, in alludiDg to his former papers on the subject, read before the 

 Section last year, at Cheltenham, stated that the subject of the mechanical or 

 dynamic force required to raise a given quantity of "water one degree of Farenheit 

 had been the object of the research of philosophers, ever since Count Rum- 

 ford, in his celebrated experiments on the evolution of heat in boring guns when 

 surrounded by ice or water, proved the power required to raise one pound of water 

 ODe degree, and which he valued at the dynamic equivalent of 1,034 lbs. M. Moya 

 was the first who announced that heat was evolved from agitated water. The 

 second was ijr. Joule, who announced that heat was evolved by water passing 

 through narrow tubes, and by this method each degree of heat required for its 

 evolution a mechanical force of TVO lbs. Subsequently in 1845 and 184'7 hje arriv- 

 ed at a dynamical equivalent of 772 lbs. These experiments had since been con- 

 firmed by other philosophers on the Continent. In the present paper Mr. Rennie 

 stated his attention was called to the subject by observing the evolution of heat 

 by the sea in a storm, and by the heat from water running in sluices. He, there- 

 fore, prepared an apparatus similar to a patent churn, somewhat resembling that 

 adoiated by Mr. Joule, but on a large scale. In the first case he experimented on 

 fifty gallons, or 500 lbs. of water, inclosed in a cubical box, and driven by a steam 

 engine instead of a weight falling from a given height, as in Mr. Joule's experi- 

 ment; secondly, on a smaller scale, by 10 lbs., of water inclosed in a box. The 

 large machine or churn was driven at a slow velocity of eighty-eight revolutions 

 per minute, and the smaller machine at the rate of 232 revolutions per minute, so 

 that the heat given off by the water in the large box was only at the rate of three 

 and a half degrees per hour, including the heat lost by radiation ; whereas the 

 heat evolved by the ten gallons of water contained in the small box agitated at 

 232 evolutions was fifty-six degrees Fahrenheit per hour. Thus the temperature 

 of the water in the large bos was raised from sixty degrees to 144 degrees, and 

 the temperature of the water in the small box to boiling point. As an illustration, 

 an egg was boiled hard in six minutes. The mechanical equivalent in the first 

 case was found to approximate nearly to that of Mr. Joule, but in the latter case it 

 was considerably above his equivalent, arising, very probably, from the difiiculty 

 of measuring aecui'ately the retarding forces. 



ON SOME PHENOMENA IN CONNEXION WITH MOLTEN SUBSTANCES. BT ME. J. NASMTTH. 



The author stated, on introducing the above subject to the notice of the Section, 

 that his object in so doing was to direct the attention of scientific men to a class of 

 phenomena which, although their main features might be familiar to practical 

 men, yet appeared to have escaped the attention of those who were more engaged 

 in scientific research. The great fact which he desired to call attention to is com- 

 prised in the following general proposition, — namely, that all substances in a molten 

 eondition are specifically heavier than the same substances in an unmolteu state. 

 Hitherto water has been supposed to be a singular and special exception to the 

 ordinary law, — namely, that as substances were elevated io temperature they be- 

 came specifically lighter, that is to say, water at temperature 32° on being heated 

 does on its progress towards temperature 40° become more dense and specifically 

 heavier until it reaches 40", after which, if we continue to elevate the temperature, 



