10 Climate. 



and even temperate regions, the variety is great, and their value 

 unquestionable. Indeed such is the effect of cold, that while 

 the thermometer is below 40, the strongest plants become 

 torpid, and remain in that state so long as this low degree of 

 temperature continues ( I ) . Revived by the warmth of spring, 

 and strengthened by the heat of summer, they acquire fresh 

 life and vigour, and are thus better enabled to withstand the 

 rigours of the succeeding winter. 



Heat is essential for bringing every plant, fruit, or species 

 of grain, to perfection. Hence, an increased temperature, 

 when not carried to excess, will augment the quantity of nu- 

 tritive matter in a plant, or improve the quality of fruit grown 

 under its influence. Thus English barley, of equal weight, is 

 more valuable than Scotch barley, because, from growing in 

 a warmer climate, and enjoying the advantage of a greater 

 quantity of light, it is more fully ripened. It thence acquires 

 more saccharine matter, and produces a greater quantity of 

 spirits, or of malt liquor ( I! ). 



It is also proved, by the experiments of Sir Humphry Davy, 

 that wheat ripened in a more regular and warmer climate, 

 contains more of that valuable substance called gluten, than 

 the same species of grain, when raised in England. 



The medium, or average heat of the year, is not, however, 

 of so much importance to the growth of plants, as its duration, 

 and its continuing steady at a certain degree, during the season 

 when the grain is ripening. This gives the uniform climates 

 of the Continent, a great advantage over our variable seasons, 

 in the production of the more delicate sorts of fruit ; which, 

 in this island, are often injured by the frosts in spring, and 

 seldom ripen perfectly in a climate, where the greatest sum- 

 mer heat is both unsteady, and of short duration ( Iz ). 



3. Light. The quantity of solar light which a climate 

 furnishes, is likewise an important object of inquiry. It is 

 ascertained that roots, not having the advantage of light, are 

 not so wholesome an article of food, as the various species of 

 grain. Plants will grow in the dark, as in mines or cellars ; 

 but in such situations, the colour of their leaves is not vivid, 

 and their seed is not brought to perfection. They have such 

 an affinity to light, that if put into a dark place, they will al- 

 ways bend to any hole or window where it is admitted ( l3 ). 

 Light is essentially necessary for increasing the proportion of 

 starch or farina ; completing the formation of oils in plants ; 

 and giving to fruits their proper colour, and flavour. It has 

 also the effect of augmenting saccharine matter, insomuch that 

 those sugar-canes which are exposed to the sun, have more 



