OBSERVATIONS OF HALES ON THE BLIGHT IN HOPS. 39 



portion, on account of the small hemisphere of eurth the new-planted, shortened 

 roots occupy ; and on account of the loose position of the new-turned earth, which 

 touches the roots at first but in few points." 



HALES proves the influence of suppressed evaporation by the following observa- 

 tions on hop-vines. 



" Now there being 1,000 hills in an acre of hop-ground, and each hill having 

 three poles, and each pole three vines, the number of vines will be 9,000 ; each 

 of which imbibing four ounces, the sum of all the ounces, imbibed in an acre in a 

 twelve hours' day, will be 36,000 ounces = 15,750,000 grains = 62,007 cubic 

 inches, or 220 gallons ; which divided by 6,272,640, the number of square inches 

 in an acre, it will be found, that the quantity of liquor perspired by all the hop- 

 vines, will be equal to an area of liquor, as broad as an acre, and yJ T part of an 

 inch deep, besides what evaporated from the earth. And this quantity of moisture 

 in a kindly state of the air is daily carried off in a sufficient quantity to keep the 

 hops in a healthy state ; but in a 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 

 good measure the kindly perspiration of the leaves, whereby the stagnating sap 

 corrupts, and breeds mouldy fen, whicb often spoils vast quantities of flourishing 

 hop-grounds." 



" This was the case in the year 1723, when ten or fourteen days' almost con- 

 tinual rains fell, about the latter half of July, after four months' dry weather ; 

 upon which the most flourishing and promising hops were all infected with mould 

 or fen, in their leaves and fruit, whilst the then poor and unpromising hops escaped, 

 and produced plenty ; because they, being small, did not perspire so great a quan- 

 tity 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 cut as fast as if it were in a hot-bed ; and the apples grew so preci- 

 pitately, that they were of a very fleshy constitution, so as to rot more remarkably 

 than had ever been remembered."* 



44 The planters observe, that when a mould or fen 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." 



44 1 have in July (the season for fire-blasts, as the planters call them) seen," 

 says HALES, " 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 plenti- 

 fully, as to make a clear and distinct object become immediately very dim and 

 tremulous. Nor was there any dry gravelly vein in the ground, along the course 

 of this scorch. It was, therefore, probably owing to the much greater quantity of 

 scorching vapors in the middle thanoutsides of the ground, and that being a denser 

 medium, it was much hatter than a more rare medium." 



44 This is an effect which the gardeners about London have too often found to 

 their cost, when they have incautiously put bell-glasses over their cauliflowers 

 early in 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 there form a 

 dense, transparent, scalding vapor, which burnt and killed the plants." 



When these observations are translated into our present language, we perceive 

 with what acuteness and accuracy HALES recognized the influence of evaporation 

 on the life of plants. 



According to him the development and growth of the plant depends on the 

 supply of nourishment and moisture from the soil, which is determined by a certain 



* Observations of Hales on the slight in hops and other plants. 



