Recent Publications on Manures. 81 



great results may be expected ; if not accompanied by these, 

 we may have much appearance, with little reality. It is generally 

 found that there is little difference in the present effects of nitrate 

 of soda and potash on the crop. As potash is, however, the base 

 which the vegetable acids generally prefer, it should be more 

 beneficial as a constituent of the plant: as a solvent of unde- 

 composed matter in the soil, the soda, when excreted, should be 

 more active and powerful. Nitrate of lime being most easily 

 produced artificially (there is generally a good deal among the 

 other nitrates), and being one of the most soluble of salts 

 (its attraction for moisture being so great as to cause it to be 

 used in the drying of gases), should also be of great benefit. 

 It possesses the same quantity of nitric acid as the others; and 

 the other salts of lime being very insoluble (the carbonate of 

 lime requiring carbonic acid in the water to dissolve it), this salt 

 may be one of the natural sources of lime to the plant. M. Jac- 

 quelaine, Professor Dumas says, has- lately found pectinate of 

 lime in the ligneous tissue of most plants ; and perhaps more of 

 that substance is needed for plants than is generally imagined. 



On guano, or bird's dung, a manure long ago introduced 

 into chemical works, but only lately become an article of com- 

 merce in this country, Mr. Squarey has amassed a good deal of 

 information, and for which recourse should be had to the book 

 itself. ". The date of the discovery of guano," he says, " is un- 

 known, though it has been used as a manure in Peru from 

 great antiquity. The immense quantities in which it exists, its 

 weight, red colour, and the sand which covers it, have caused 

 it to be thought of mineral origin. That most recently depo- 

 sited, however, is white, and most in demand, but gets red by 

 exposure to the air, and the sand blown from the hills around ; 

 the ammoniacal odour also which it gives off, and the uric, phos- 

 phoric, and other acids found in it, determine it to be of animal 

 origin. It has also been observed that, when the birds have been 

 scared away from any place on the coast, the supply has dimi- 

 nished in that place. In the dry climate of Peru, the excrement 

 of the birds is not washed away, as in our damp atmosphere. 

 In some places it is represented as existing to the extent of a 

 quarter of a league in length, and 300 yards in depth. The red 

 and dark grey guano," he says, " is sold at 2s. 3d. per cwt., and 

 the white at 3s. 6d. per cwt., in the port of Mollendo ; in war it has 

 sometimes been as high as 12s. The guano," he says, " is strono-ly 

 recommended for wheat, barley, oats, turnips, and clover." 

 The quantity per acre he recommends is 1 to 2 cwt., mixed 

 with charcoal powder; price in London, Nov. 1841, 26s. per 

 cwt. The excellence of this manure, he says, " depends in great 

 measure on the phosphate of lime it contains, which he esti- 

 mates at 30^ per cent, the lithic acid and ammonia at 30, and 

 3d Ser.— 1842. II. g 



