TEMPERATURE AND METEOROLOGY. 
129 
iiall we say of a third — Magnetism ? Can we doubt its identity when we are 
irtified of the earth’s magnetic power? And here another suggestion presents 
self. — Is not cold a substantive essence — a positive entity — and not the mere absence 
heat? Why may it not be referred to magnetism, since the magnetic poles are, 
ijyond doubt, referable to the coldest and most frozen regions of the globe? Again, 
I ; a fourth, we recognise the chemical principle to which so much importance is now 
;tached that the term actinism has been applied to it, while its effects and the 
,udy of it have been distinctively called actino -chemistry. 
This curious principle is described in Mr. Robert Hunt’s “Treatise on the 
hysical Powers of the Universe,” as “ one of the greatest powers of creation.” 
early all, if not all, the phenomena of change, which have been referred to light, 
*e now proved to be actinic powers ; and beyond the influence which is exerted by 
j. upon all inorganic bodies, that of the solar beams on vegetation is proved by 
)mmon experience. Other principles — called, by Sir John Herschel, Parathermic 
I iys — are here alluded to : “ they act partly as light, and partly as heat, yet with 
istinguishing difference.” 
It is always wise to recur to authorities where any difficult subject requires 
iscussion : the progress of science is slow, men oppose each other through a spirit 
f pure opposition, which not merely obstructs, but actually falsifies their own minds, 
j leretofore, since the discoveries of Dr. Black, the doctrine of latent heat has been 
, ertinaciously maintained. Now, however, we begin to admit that heat, light, 
I lectricity, magnetism, and chemical power, are just so many substantive emanations 
:om the sun. He then, the Fountain of Light, radiates, or transmits these 
italising elements to the earth, which thus becomes the great elaborating medium, 
herein all the operations that terminate in meteorological phenomena are per* 
mned. Subject to these considerations, what are the principles which should be 
dopted in the construction of our forcing-houses ? If, as has been said, solar 
| ower produces equability of heat, should it not be the aim of the forcing gardener 
p adopt a method by which any erection that occasionally or generally requires 
: rtificial excitement, can be heated throughout its entire area with all attainable 
egularity ? 
Yet, whether we consider the old fire-flue, the complicated steam apparatus, the 
ot-water pipes, channels, and tanks, the same results present themselves; for 
regularity of temperature, even to the amount of many degrees, is discovered in 
11 of them. 
In a twenty-four feet house, attempted to be warmed as a vinery by a double 
ourse of hot- water channels, made of twelve-inch square paving-tiles cemented, that 
•assed on every side of the erection, the air could never be regularly heated ; its 
emperature varied fully five degrees, and even then the utmost power of a furnace 
fhich consumed two bushels of coke in twenty-four hours, could not insure 65° 
t the entrance of the “ flow ” water, during a severe frost, thus rendering it 
lifficult to obtain more than 59° at the distance of twelve feet from that entrance. 
VOL. XIV. NO. CLXII. s 
