ON CONCENTRATED INFUSIONS. 
259 
but it must not be overlooked that the process by which these extracts are 
obtained is calculated to preserve the activity of the plant,—for extractive matter, 
if oxidized, ceases to be soluble. 
The soil of Mitcham is generally a good holding one, that is, retains moisture 
well, and is naturally rich. It varies in depth even on the same estate, being 
in some places only a few inches, whilst in others it is several feet. 
Most growers supply large quantities of manure to their land, but evidently 
do not supply the elements abstracted by the growing crops, as the yield is con¬ 
tinually diminishing. They do not lay out for two successive seasons the 
same plants on the same ground. This is axiomally admitted by them to be as 
desirable as the rotation of agricultural crops. Some growers plant potatoes, etc., 
after peppermint; and, after renewing the soil with manure, again plant pepper¬ 
mint. This plan is considered highly beneficial to the production of good crops. 
The uncertainty of the seasons in England, and the introduction of foreign 
produce, have considerably reduced the annual production of Mitcham. A large 
farm, consisting of more than 1000 acres, which was a few years ago laid out 
with Lavender, Peppermint, lloses, Chamomiles, Caraways, and Henbane, is 
now employed entirely for the production of cereal crops; and most growers, 
rather than meet with the disappointment of a failure, lay out a large propor¬ 
tion of their land with culinary vegetables. 
The flowers obtained during a very dry season such as the past, yield a larger 
proportion of oil than the flowers obtained during an ordinary summer ; but, 
from the combined effects of the frosts during the latter part of May, less oil will 
be obtained this year than for years past. The yield of Oil of Lavender will be 
from 4 lb. to 5 lb. per acre. 
I have intentionally omitted to include in this paper the analyses of the soils, 
as I consider them more intimately connected with the phenomena of cultivation 
when considered in reference to physiological effects, and which I intend to lay 
before the conference in a paper on “The Effects of Soil and Cultivation on 
the Development of the Active Principles of Plants.” 
ON THE PREPARATION OE SMALL QUANTITIES OF 
CONCENTRATED INFUSIONS. 
BY MR. T. GRUNDY. 
(Read at the Bath Meeting of the British Pharmaceutical Conference , Sept. 18GI.) 
The subject of concentrated infusions has been so often treated, that there 
is but little new to be said about them. I have, however, used a process for 
making them which has given me satisfactory results ; and as it is applicable 
to a pint of infusion, I think it will answer the question proposed to the Con¬ 
ference. It is, of course, needless to point out that no concentration can 
exactly represent the infusions of the Pharmacopoeia, on account of the ne¬ 
cessary employment of spirit, to keep the product. Personally, I hold the 
opinion that a concentrated infusion, when ^oell made, is superior to a fresh 
infusion, and answers the purpose of a chemist better; but the authorities on 
the other side are numerous and important. 
The principle on which I proceed is that of hot percolation. I have had a 
percolator made of tin, being a double tin drum, with an inlet pipe at the 
bottom, and a small jet at the top ; the bottom pipe is then connected with a 
little tin boiler placed over the gas. Steam is generated in the boiler and 
passes into the casing of the percolator, blowing off at the little jet at the 
top. The bottom of the percolator is made of wire gauze, on which a piece 
