148 Comparative Temperature of different Years, 



average temperature of London is 50-4?°, and that the hottest or 

 coldest seasons we experience do not materially affect this 

 average, seldom causing it to vary even half a degree. And when 

 we consider that it is nearly impossible to ascertain correctly 

 the actual amount of temperature during a season, we may 

 almost conclude that in this respect years are invariably alike, 

 and that the (to us) incomprehensible machinery of the weather 

 is regulated with incontrovertible precision, the very air we 

 breathe " weighed as in a balance." However, for every pi'ac- 

 tical purpose, it will be sufficiently accurate to assume that, so far 

 as regards temperature, years are invariably alike, and that in a 

 given time we may depend upon receiving a stated quantity. 

 Now the heat of every season being alike, and the effects pro- 

 duced so different, the difference must proceed from the manner 

 of its application : and it is by narrowly observing that man- 

 ner, that we may glean useful information enabling us to ame- 

 liorate the condition of even external objects ; but, these being 

 placed in circumstances in a great measure beyond our con- 

 trol, our operations must of necessity be limited. Therefore 

 it is to the manager of artificial climates, who has all the requi- 

 sites (light excepted) under his immediate control, that the 

 information gained from such observations must prove most ex- 

 tensively useful. 



It requires no hesitation to say that hot summers are 

 most desirable. For the production of these, the preceding 

 winters must have been sufficiently severe to create a deficiency 

 that demands a proportionate excess to supply ; consequently 

 weather in extremes is most congenial to the vegetable produc- 

 tions of the earth, a fact that has not escaped even the unlet- 

 tered cultivator of the soil, who may often be heard deploring 

 the loss of hard (or as he terms them " old-flishioned") winters. 

 Mild winters, by an excess of temperature, preclude the possi- 

 bility of hot summers, and prove hurtful to vegetation, by ren- 

 dering winter and summer too much alike, depriving the plants 

 of absolute rest, by causing them to spend the time that ought 

 to be devoted to such a purpose in a semi-torpid state, the after 

 lano-uid excitement consequent upon such a state of things being 

 insufficient perfectly to rouse them from their lediargic condition. 

 A state of absolute rest is a provision of nature that seems indis- 

 pensable to the well-being of many of the vegetable productions 

 of a rigorous climate, where existence in a state of excitement 

 during times of severity is incompatible with their organisation ; 

 and, whatever the necessity for its return at a stated period, the 

 term of its duration is indefinite, varying considerably even when 

 left to nature, and can be shortened or altered almost at plea- 

 sure by the hand of art, as it requires only a proper degree of 

 heat to call their suspended powers into action at anytime that 



