RULE FOR CONSTRUCTING CHIMNEYS, ETC. 
279 
then, that the crude bones cost £4 per ton, the 
same quantity, as prepared by Mr. BJackhall's pro- 
cess, would cost £5, 65. 8d.. independently of the 
cost of steaming. Tt is true that the whole quan- 
tity of the phosphate of lime will remain in the 
bones, but it must be recolieded that the gelatine 
which is extracted is a very valuable manure, and 
extremely rich in nitrogen, so much so that Bous- 
singault, who has given a comparative table of the 
value of manures, founded upon the amount of 
nitrogen they contain, estimates, (irrespective of 
the phosphate of lime,) six parts of bones as 
equivalent to 100 of farmyard manure. Now, by 
Mr. Blackhall's method, the animal matter extract- 
ed must be entirely lost, or it must be recovered 
by evaporating the condensed steam, or, in the 
event of the quantity of water being sufficiently 
small, by converting it into a compost. Any such 
operations, however, must, to a greater or less ex- 
tent, add to the original cost of the bones. 
Tt is quite possible that, by the use of a proper 
steaming vessel, the quantity of gelatine extracted 
may be reduced considerably under what it was in 
either of the specimens analysed, but it admits of 
question whether this very extraction may not be 
connected with the softening process. It is well 
known, at least, that bones, from which all or 
nearly all the animal matter has been extracted by 
boiling in water under pressure, are so soft that 
they may be reduced to fine powder by rubbing 
between the fingers. On the other hand, it is neces- 
sary to mention that, in an experiment performed 
by Mr. Slight, of Edinburgh, with high-pressure 
steam, of 35 lbs. to the square inch, the softening 
was not by any means so great as Mr. Blackhall 
described, as the bones retained their form, and 
required the use of a cake-breaking machine to 
reduce them to powder. 
These are disadvantages which are like to limit 
considerably the value of Mr. BlackhalPs process; 
but it ma}', notwithstanding, prove valuable in 
remote districts, where small quantities of bones 
may be collected at such a distance from a bone 
mill as to render it impossible to transport them to 
it. The superiority of steamed bones as a manure 
is a question which can be properly determined 
only by experiment in the field, and it is not impos- 
sible that good results may be obtained from them, 
though they can never form a substitute for bones 
dissolved by an acid. 
REMARKS ON THE NUTRITIVE VALUE OF 
CORN COBS. 
It is well known that the manure of an aninsal 
varies in quality with the food which it eats; and 
that generally manure is richer in nitrogen bodies, 
and less rich in non-nitrogenized matter than the 
food consumed. Probably a greater proportion of 
100 lbs. of nitrogen bodies would be assimilated by 
the system, if it were mixed with 500 lbs. of non- 
nitrogenized matter, and still more if mixed with 
1.000 lbs., than if taken into the system undiluted 
or alone. It should be borne in mind that it is as 
essential for food to contain bodies destitute of 
nitrogen, (such as starch, sugar, oil, &c.,) or those 
which go to support animal heat and respiration in 
the body, as it is for it to have nitrogen compounds 
to nourish or supply the waste of the living tissues. 
Hence food, suited best to sustain animal life, is that 
which is made up of these two classes of bodies, 
mixed in the proper proportion. And a deficiency 
in the one is equally as deleterious to the healthy 
existence of the animal as a deficiency in the other"; 
therefore we can hardly say that one of these 
classes is in reality more essential to the main- 
tenance of life than the other. They both seem to 
perform equally important offices. If this view 
be taken, the cob cannot be regarded as deficient 
in those bodies which contribute to support respira- 
tion and nutrition. 
The table below shows about the amount of the 
several proximate organic bodies thrown away in 
rejecting the cob, calculated from the analysis of 
the small white-flint variety. 1,000 lbs. of ears 
contain not far from 200 lbs. of cob and 800 lbs. 
of grain. These contain the following bodies in 
the following proportions, expressed in pounds and 
decimals of a pound-: — 
200 lbs. 
800 lbs. 
1, 000 lbs. 
Cobs. 
Grain. 
Sugar and extract, . 
13.582 
115.320 
128.902 
Starch, .... 
a 003 
487.384 
487.387 
Fiber, 
127.6S7 
7.712 
135.393 
Oil 
39.824 
39.824 
Zein 
31.855 
31.856 
Matter separated by potash 
from fiber, . 
45.404 
51.856 
97.360 
Albumen, .... 
1.518 
37.136 
33.654 
Casein, .... 
0.238 
0.688 
0.976 
Dextrine or gum, 
2.310 
28.224 
30.534 
Resin, . 
i.305 
1.806 
Glutinous matter, 
7:402 
7.402 
200 lbs. 800 lbs. 1,000 lba. 
In the above table, the inorganic matter is not 
separately considered, it being distributed among 
the several organic bodies. By rejecting the cobs 
of 1,000 lbs. of dry ears, about 200 lbs. of organic 
matter is lost, which consists of 13| lbs. of suo-ar 
and extract, 1271 lbs. of fiber, 45! lbs. of matter 
separated from fiber by a weak solution of potash, 
1 k lbs. of albumen, 0.288 of a lb. of casein, 2.3 1 lbs. 
of gum or dextrine, 1.8 lbs. of resin, and 7.4 lbs. 
of glutinous matter. Hence the cob, although not 
rich in nutritive matter, can by no means be sa ; d 
to be destitute of those proximate principles which 
go to support respiration and sustain animal heat, 
and those which are capable of being transformed 
into nerve, muscle. &c, and the phosphates which 
contribute so largely to the formation of bone. — 
N. Y. State Transactions, for 1848. 
— ♦ 
RULE FOR CONSTRUCTING CHIMNEYS. 
A very erroneous. practice prevails, among chim- 
ney builders, of contracting the passage for the 
smoke at the lower part near the fire place. " This/' 
says Treadgold, " is like contracting the aperture 
of a pipe which supplies a jet." Chimneys, to 
draw well, should be contracted at the top. The 
rule for ascertaining the required degree of con- 
traction is as follows.: — 
Let 17 times the length of the grate, in inches, 
be divided by the square root of the height of the 
chimney, in feet, and the quotient will be the area 
in inches, of the transverse section of the aperture 
at the top of the chimney. For example, a grate 
15 inches in length, with a chimney 36 feet high, 
to which the contracting top is required — 17 multi 
plied by 15 gives 255, which number divided by 6, 
the square root of 36, gives 42| inches for the area 
of the top. 
