REPORT OF THE COMMISSIONER OF AGRICULTURE. 93 
it would give off no more thick, green scum, it was run into the evaporator proper, 
which consisted of cast-iron pans on rollers. The pans were 8 feet long, 24 feet wide, 
and 6 inches deep. They were kept boiling and skimmed constantly until no more 
scum would rise. To prevent burning, it should be repeatedly stirred with a broad 
wooden ladle. No lime or chemicals were used. The degree to which the sirup is 
boiled is determined by no fixed rules. One man who has had years of experience 
does the work, and can tell when to run off by taking it up on his ladle and then run- 
ning it back into the pan. As soon as done the pan is rolled off the fire and the sirup 
is taken out and put into a cooler pan, and then run back and refilled. One heater 
will keep four such pans running. 
Some say, boil it down thick so the sirup will keep; others say, do not make it so 
thick as I did last year, for we could not get it out of the barrel. Mine was boiled 
down so thick that after getting thoroughly cold it took an hour to run a gallon into 
a jug through an inch funnel. Granulation began within two weeks. 
Besides the work of the Chemical Division herein reported, there has 
been received almost daily letters from all sections of the country ask- 
ing for advice and information concerning the various matters pertain- 
ing to agricultural chemistry, and the correspondence alone is no incon- 
siderable item of the work devolving upon this division. 
TANNING MATERIAL. 
The importance of a new and abundant source of tannin can hardly 
be overestimated. While in the oak and hemiock bark and sumac of the 
country the United States will probably have enough tanning material 
to answer their own purposes for the next generation, yet there is a 
large market in other countries, which is now supplied from very many 
sources, involving the expenditure of millions of dollars. If it is pos- 
sible to add to our agricultural exports a substance which can be pro- 
duced at a profit, and command any considerable portion of the world’s 
market for tanning materials, it is well worthy an effort on our part to 
secure, either by importation or naturalization of foreign plants, such as 
the wattle, or to utilize any that are native within our own borders for 
this purpose. The utilization of the sumac, which grows wild over so 
large an extent of our country, has been encouraged by a thorough exami- 
nation made by Dr. McMurtrie, a former chemist, and being published 
in our last report has attracted very great attention throughout the 
country, and has given an impetus to the utilization of this bush, which 
is a common growth by the way-side and in neglected and abandoned 
fields. 
A clearing out of the rooms devoted to the Chemical Division of the 
department incident to the induction of our present chemist disclosed, 
among other things which had been stowed way, evidently for years, 
the following correspondence, accompanying a parcel which apparently 
had never been opened. As there is strong probability that the root 
inclosed in this package will prove to be of great importance, the entire 
correspondence connected therewith is cited in this report: 
San ANTONIA, TEX., July 9, 1868. 
Sir: Ihave the honor to hand you herewith a copy of a letter written by John 
James, esq., of this city, in relation to the roots of the plant cailaigre, a package of 
which will be forwarded by the same mail that brings you this letter. The plant is 
found growing in the vicinity of Fort Clark, on the banks of Limpia Creek, and can 
” be cultivated to any extent in Western and Northwestern Texas, where it sometimes 
grows to the thickness of a man’s leg. 
Any quantity of hides can be obtained here, and many thousands are shipped north, 
and manufactured leather is returned to the State. If all that is claimed for the 
caniaigre is true, it is destined to effect a great change in the leather trade of Texas. 
Respectfully, 
S. P. GAMBIA, Postmaster. 
Hon. COMMISSIONER oF AGRICULTURE, 
Washington, D. C, 
