Value of Artificial Manures. 
545 
price that it costs, or that we give it credit for ; and the manu- 
facture of superphosphate of lime will be imperfect so long as 
insoluble phosphate figures as one of its ingredients. 
To justify the prices which I have adopted for different ele- 
ments of manure, I shall now give analyses of guano and super- 
phosphate of lime from my laboratory books. I begin with guano, 
of which, since the publication of my paper on that manure, a 
very great number of samples have reached me from all quarters. 
It will be remembered that the average quantity of phosphate 
of lime in Peruvian guano was formerly fixed by me at 24 per 
cent. ; and this number has been usually adopted by other che- 
mists, either from their own analyses, or on my authority. 
Since the publication of my paper on guano, it became evident 
that the methods of analysis were not so accurate as they might 
be. The reader is referred to a note at the end of this paper for 
a detailed explanation on this subject ; and it will be sufficient 
to state, that upon more refined examination, the average propor- 
tion of phosphate of lime was found to be more nearly 30 per 
cent., of which nearly 7 per cent, occurs in the state of soluble 
phosphate. This circumstance has a very material influence on 
the value of guano, and on the price of its constituents, and will, 
of course, affect the relation of this manure to other manures in 
the market. Since the commencement of the year 1852, the 
more accurate method of analysis has always been employed in 
this laboratory ; and I gladly take this opportunity of publishing 
a body of results serving still more definitely to fix the value of 
this very important manure. The following Table gives the 
analyses of a great number of samples of Peruvian guano, re- 
ceived for analysis from all quarters, but mainly from members 
of this Society, during the last four years. 
Table III. — Analyses of Genuine Samples of Peinvian Guano, 1852 to 
1855 inclusive. 
No. of 
Sample. 
Moisture. 
Organic 
Matter 
and 
Salts of 
Ammouia 
Sand. 
Phos- 
phates of 
Lime 
and 
Magnesia. 
Alkaline 
Salts. 
Nitrogen. 
Equal 
to 
Ammonia 
Phos- 
phoric 
Acid in 
Alkaline 
Salts. 
Equal to 
Soluble 
Phos- 
phate of 
Lime. 
1 
IS- 
36 
47-27 
1- 
43 
23-57 
9- 
37 
IS- 
73 
16- 
67 
3-72 
7-67 
2 
IS 
83 
51-64 
1 
44 
23*48 
9 
61 
IS- 
18 
16 
00 
3-70 
7-62 
3 
13 
44 
52-66 
1- 
58 
21-30 
11 
02 
14 
46 
17- 
55 
3-34 
6-88 
4 
15 
23 
49-73 
2 
63 
21-63 
10 
78 
13 
04 
15- 
83 
3-74 
7-71 
5 
14 
64 
51-37 
2 
16 
23-41 
8 
42 
14 
43 
17 
52 
3-35 
6-90 
6 
14 
22 
49-83 
3 
32 
19-30 
13 
33 
13 
43 
16 
30 
2-84 
5-85 
7 
14 
27 
52-12 
1 
34 
22-41 
9 
86 
14 
03 
17 
04 
3-14 
6'47 
8 
13 
05 
52-57 
1 
70 
22-62 
10 
06 
14 
24 
17 
29 
4-87 
10-04 
9 
15 
25 
51-84 
2 
74 
21-04 
9 
13 
13 
78 
16 
73 
3-87 
7-97 
10 
14 
71 
48-93 
2 
19 
21-59 
12 
58 
12 
73 
15 
45 
3-19 
6-57 
11 
12 
48 
51-93 
1 
99 
22-38 
11 
22 
13 
55 
16 
45 
3-27 
6*74 
