514 
The turpentine is not to be obtained in considerable quantities from very young trees, and in old 
ones it gradually dries up, till at last it affords none: it is only after the tree has attained the thick¬ 
ness of ten or twelve inches in diameter, that it is thought worth while to collect the turpentine; and 
from that time, during forty or fifty years, if it continues so long in vigorous growth, the tree will 
continue to yield annually from seven to eight pounds of turpentine. 
An English acre will contain six hundred and eighty-two trees, at the distance of eight feet 
from each other. Suppose the annual produce to be six pounds a tree on an average, and the 
price to be no more than two-pence the pound, (the common turpentine that the painters use is now, 
1799j six-pence a quart,) the value of the produce would be 31. 4s. 2d. the acre; on supposition 
that the trees would yield as much turpentine in Britain, as on the borders of the Adriatic gulf 
Whether they will do so, remains to be ascertained by experiment. 
Besides this well known product the Larch yields also a Manna and a Gum. The Manna is 
found in the South of France, and is called there Marine de Briancon: it is white, concrete, and 
sweet, like fine new honey. It is rare, and met with only in little drops, so that it would be very 
difficult to collect a pound of it. The drops are more or less hard, and adhere to the leaves. 
Mons. Villars having made some enquiries relative to this substance with Mons. Guettard in 
the year 1773, found it at sun-rise almost fluid; and picked up drops of it on the turf exactly like 
those which remained on the trees; but they have not given any analysis or farther account of it, 
except that the season of 1773 was less productive of Manna than usual * Last year (1798) I 
observed a Larch near my house covered with a hoary powder, but I neglected to examine whether 
it had any of the qualities of Manna. In the present year there is no appearance of it. The last 
season was a hot dry one, and therefore favourable to the production of Manna; and the season of 
1799 has been a cold wet one. 
Pallas informs us that they have this Manna in the Russian empire, but that it is rarely found 
concrete, being commonly soon washed off by the rains which are frequent on the Uralian 
mountains. 
He remarks also, that the turpentine resides in the bark and the wood next to it, as is apparent 
when the trunk of a Larch is sawed transversely; for then it may be seen that the inner wood for 
more than half the diameter is dry. It cannot therefore be of any use to drive the auger almost to 
the centre of the tree, as Dr. Anderson recommends. 
Pallas also mentions a Gum that is yielded by the Larch in particular circumstances. When 
the woods are on fire, which frequently happens in Russia, the Larches are easily burnt on the side 
next the flame to the height of several feet, on account of the turpentine with which they abound. 
If the wood happens to be scorched to the pith, the inner part exudes a dry, reddish gum, rather less 
glutinous than Gum Arabic, having a slight taste of resin, but wholly soluble in water. It is used 
in medicine; and the native mountaineers chew it to fasten their teeth, as an antiscorbutic, and as 
a substance highly nutritive; they also use it as a glue to fasten their bows, &c. 
The Siberian hunters of Ermines, when their ferment or yest which they carry with them to 
make the acid liquor which they call Quass with, is spoiled by the cold, scrape off the albumen or 
half-formed wood between the bark and the wood, which is very juicy and sweet, digest it with 
water over the fire during an hour, mix it with their rye meal, bury the dough in the’snow, and after 
twelve hours find the ferment ready prepared in the subsiding feces.f 
Old Larches produce a Fungus, which is described very much at large by Jacquin, in the first 
* Plantes de Dauphine, 3. 808. 
i" Flora Rossica, 1. p. 2, 3. 
