H E A 



Hence may be explained the phenomenon of the Harvest Moon, pre- 

 mising that when the 1st point of Aries rises, the ecliptic makes the least 

 angle with the horizon. For if the moon's orbit be supposed to coincide 

 with the ecliptic (which it does nearly) sin. n is least when the moon 

 rises in Aries ; therefore the numerator of the above expression is then 

 least; and because cos.* S 1, the denominator is then greatest; .". on 

 both accounts D is least, and if the sun be at the same time in Libra, the 

 moon is then at the full ; therefore the full moon, which takes place near 

 the autumnal equinox rises nearly at the same time for several nights, 

 and as this is near the time of harvest in north latitudes, it is called the 

 Harvest Moon. 



HEAT, various Tables relating to. 



TABLE I. 



Table oftJie effects of heat on different substances according to Fahrenheit'* 

 thermometer and Wedgwood's. ( Wedgwood.} 



Fahr. Wcdg. 



Extremity of the scale of Wedgwood ~~+ 32277 240o 



Greatest heat of his small air furnace 21877 160 



Chinese porcelain softened . ^^, 156 



Cast iron melts .^ 17977 130 



Greatest heat of a common smith's forge *~~ 17327 125 



Derby porcelain vitrifies ~~> *~~ 1 12 



Welding heat of iron greatest ,~~ 13427 95 



least 12777 90 



Fine gold melts ,~~ 5237 32 



Fine silver melts +~~ ~~~ 4717 28 



Swedish copper melts ~~~ ^~, 4587 27 



Brass melts ~~* 3807 21 



Enamel colours burnt. on ~~ ~~~ 1857 6 



lied heat fully visible in day light *~* 1077 



in the dark ,~~ 917 1 



Mercury boils 600 3^ 



Water boils 



Vital heat 



Water froo/ps ^^ *~~ *^* 



Proof spirit fre2CS ,*** ~*~ mw M 



m H a 



