PROTECTION FROM ATMOSPHERICAL INJURIES. 357 



Manuring. Permanent manures, such as stable-dung and other solid 

 substances, are for the most part incorporated with the soil when it is 

 dug or trenched before being cropped, and it is generally thought that 

 most advantage may be obtained from them when they are deposited 

 near the surface. Temporary manures, such as soot, bone-dust, and 

 other powders, waste yeast (one of the richest of manures), and liquid 

 manures, such as drainings of dung, and solutions of salts of different 

 kinds, and town sewage (which is one of the best fertilizers), are most 

 advantageously applied on the surface of the ground, and to growing 

 crops. The unusually heavy crops which have been raised from town 

 sewage are proofs of its enormous force as a producer of food. 



Blanching. 



The operation of blanching, or depriving the leaves and stems of 

 plants of their green colour, is effected by excluding light from the 

 growing plant, in consequence of which it is produced without colour, 

 and without that portion of its flavour which depends on colour. The 

 tubers of potatoes are blanched naturally, because in general they are 

 produced under the surface of the soil, or they are shaded by the foliage of 

 the plant. Celery is blanched as it grows, or after it has grown, by draw- 

 ing up earth so as to cover the petioles of the leaves. The leaves of the 

 cardoon are blanched in a similar manner, and sometimes by tying them 

 round with ropes of hay or straw. The interior leaves of the common 

 cabbage, and of the cabbage-lettuce and endive, are blanched naturally, 

 but the process is sometimes heightened by tying up the leaves, and 

 sometimes by coverings. In general, perennial plants in which the 

 nutriment for the leaves of the coming year has been deposited in 

 the roots during the year preceding, such as the asparagus, sea-kale, 

 chicory, &c., may be blanched by covering them entirely either with 

 soil or some kind of utensil; while annual plants, the leaves and 

 every part of which are the produce of the current year, require to have 

 the operation performed by degrees as the leaves advance in size, 

 whether by tying up, earthing up, or by both modes. By the opera- 

 tion of tying up, two effects are produced : the inner leaves as they 

 grow, being excluded from the light, are blanched ; and being com- 

 pressed, in proportion to their number and the degree of growth which 

 takes place after tying up, the head of leaves becomes at once tender 

 and compact. Perennial and biennial plants with branching roots may 

 be blanched on a large scale, by placing the roots in soil in a cellar or 

 dark room ; but this cannot be done with annual plants, which must 

 be grown in light, and blanched as they grow. 



Protection from Atmospherical Injuries. 



The great number of plants cultivated in this country, even in the 

 open air, many of them from climates very different from ours, have 

 given rise to a variety of contrivances to protect them from atmo- 

 spherical injuries. The most effective of these is without doubt that of 



