340 APPENDIX C. 



rainy moist state of air, without a due mixture of dry weather, too 

 much moisture hovers about the hops, so as to hinder, in a great 

 measure, the kindly perspiration of the leaves, whereby the stag- 

 nating sap corrupts and breeds mould. 



' This was the case in the year 1723, when ten or fourteen days 

 almost continual rains fell", about the latter half of July, after four 

 months' dry weather ; upon which the most flourishing and prom- 

 ising hops were all infested with mould in their leaves and fruit, 

 while the then poor and unpromising hops escaped and produced 

 plenty ; because they being small, did not perspire so great a 

 quantity as the others ; nor did they confine the perspired vapor 

 so much as the large thriving vines did in their shady thickets. 



' This rain on the then warm earth made the grass shoot out as 

 fast as if it were in a hotbed ; and the apples grew so precipitately, 

 that they were of a very fleshy constitution, so as to rot more re- 

 markably than had ever been remembered. 



' The planters observe, that when mould has once seized any 

 part of the ground, it soon runs over the whole, and that the grass 

 and other herbs under the hops are infected with it ; probably 

 because the small seeds of this quick growing mould, which soon 

 come to maturity, are blown over the whole ground ; which 

 spreading of the seed may be the reason why some grounds are 

 infected with fen for several years successively. 



' I have,' says Hales, ' in July (the season for fire-blasts, as the 

 planters call them), seen the vines in the middle of a hop ground 

 all scorched up, almost from one end of a large ground to the 

 other, when a hot gleam of sunshine has come immediately after 

 a shower of rain ; at which time the vapors are often seen with 

 the naked eye, but especially with reflecting telescopes, to ascend 

 so plentifully as to make a clear and distinct object become imme- 

 diately very dim and tremulous. ISTor was there any dry gravelly 

 bed in the ground, along the course of this scorch. It was, there- 

 fore, probably owing to the much greater quantity of scorching 

 vapors in the middle than outside of the ground, and that being a 

 denser medium, it was much hotter than a more rare medium. 



' The gardeners about London have, to their cost, too often had 

 occasion to observe a similar eifect, when they have incautiously 

 put bell-glasses over their cauliflowers early on a frosty morning, 

 before the dew was evaporated off them ; which dew being raised 

 by the sun's warmth, and confined within the glass, did then form 

 a dense transparent scalding vapor, which burnt and killed the 

 plants.' 



These observations translated into the language of the present 

 day clearly show how acutely and exactly Hales comprehended 

 the influence of perspiration upon the life of plants. 



According to him, the proper thriving of plants depends upon 

 the supply of food and moisture from the soil, which again is gov- 

 erned in a measure by a certain temperature and dry ness of the 



