Curiosities of Science. 189 



with the exception of a burnish of gold leaf, the thickness of 

 which cannot amount to the two-hundred-thousandth part of 

 an inch. Transactions of the Royal Society of Edinburgh. 



EXPANSION OF SPIRITS. 



Spirits expand and become lighter by means of heat in a 

 greater proportion than water, wherefore they are heaviest in 

 winter. A cubic inch of brandy has been found by many ex- 

 periments to weigh ten grains more in winter than in summer, 

 the difference being between four drams thirty-two grains and 

 four drams forty-two grains. Liquor-merchants take advan- 

 tage of this circumstance, and make their purchases in winter 

 rather than in summer, because they get in reality rather a 

 larger quantity in the same bulk, buying by measure. Notes in 

 Various Sciences. 



HEAT PASSING THROUGH GLASS. 



The following experiment is by Mr. Fox Talbot: Heat a 

 poker bright-red hot, and having opened a window, apply the 

 poker quickly very near to the outside of a pane, and the hand 

 to the inside ; a strong heat will be felt at the instant, which 

 will cease as soon as the poker is withdrawn, and may be again 

 renewed and made to cease as quickly as before. Now it is 

 well known, that if a piece of glass is so much warmed as to 

 convey the impression of heat to the hand, it will retain some 

 part of that heat for a minute or more ; but in this experiment 

 the heat will vanish in a moment : it will not, therefore, be the 

 heated pane of glass that we shall feel, but heat which has come 

 through the glass in a free or radiant state. 



HEAT FROM GAS-LIGHTING. 



In the winter of 1835, Mr. W. H. White ascertained the tem- 

 perature in the City to be 3 higher than three miles south of 

 London Bridge; and after the gas had been lighted in the City 

 four or five hours the temperature increased full 3, thus mak- 

 ing 6 difference in the three miles. 



HEAT BY FRICTION. 



Friction as a source of Heat is well known : we rub our 

 hands to warm them, and we grease the axles of carriage- wheels 

 to prevent their setting fire to the wood. Count Rumford 

 has established the extraordinary fact, that an unlimited sup- 

 ply of heat may be derived from friction by the same materials : 

 he made great quantities of water boil by causing a blunt borer 

 to rub against a mass of metal immersed in the water. Savages 

 light their fires by rubbing two pieces of wood : the modus opcr- 



