Mr. R. endeavoured to make us comprehend the causes of all those changes which have appeared so contradictory. “In the first place,” said he, “tabasheer is a remarkably porous substance; now if one of the pores be filled with air, a ray of light in passing through it suffers very little refraction, and is therefore so little scattered, that the tabasheer appears transparent, and objects can be partly seen through it. This arises from the small difference between the refractive power of air and of tabasheer. Next,” said he, “suppose a very small quantity of water introduced into this pore, so as not to fill it, but merely to line it with a film; then the light, in passing through the tabasheer, the film of water, the air within, the film again, and lastly the tabasheer, is so much scattered by these six refractions, that the substance appears opaque. But when by complete immersion the pores are filled with water, the multiplied refractions caused by the films and the portions of air within, cease, and the light is more freely transmitted.”
My uncle and Mr. R. talked a long time on the subject, and tried several other experiments, explaining to us the reasons for each step they took; but I have said enough to shew you that I endeavoured to understand what they were doing, and this I am sure will give you pleasure. Indeed the advantages of being able to comprehend something of the conversation of such people is so great, that I cannot sufficiently thank you for having given me a little taste for science. You used to say that there was great danger of making girls conceited by giving them a smattering of science; but I assure you that I shall keep a careful watch over myself in that respect; the little knowledge I have is only a peep-hole through which I see the boundless stores that I can never hope to possess—and surely this can only make me more humble.
Nov. 1st.—I had not time yesterday to say any thing of the plant which produces the tabasheer; and perhaps Marianne might like to have the particulars that we were told.
It is the bamboo-cane, which is of the same natural order as the grasses; it grows in both hemispheres, almost anywhere within the tropics, and very abundantly in the East Indies. The main roots are thick and jointed, and from these joints spring several stems, which are sometimes eighteen inches in circumference at the bottom. These stems or culms are round, hollow, and shining; they grow quite straight, and often to the height of sixty feet; and they are articulated, or knotted; the knots being about a foot apart, and each armed with one or two sharp spines. The leaves are narrow, eight or nine inches long, and supported on short foot stalks; and the flowers grow in large panicles, three or four together, from the joints of the stem.
The stalks of the bamboo, while young, are filled with a spongy substance which contains a sweetish milky juice; but they become hollow as they grow old, except at the joints, where they are crossed by a woody membrane—such as I believe there is in the knots of all culms. Upon that membrane the liquor rests, and concretes into the substance called tabasheer, or sugar of Mombu—which was held in such esteem by the ancients, that it was valued at its weight in silver. It had long been used as a medicine all over the east, but was first made known in Europe by Dr. Russell in 1790.
The young shoots are dark green; and, while tender, make a good pickle; but the old stalks are of a shining yellow colour, and prodigiously hard and durable: they are used in buildings, in all the farming tools, and in all sorts of household furniture. By piercing the joints they are often converted into water-pipes, and they make excellent poles by which the porters carry casks, bales, and palanquins. In the island of Java, a sort of palanquin is formed of bamboos, resembling a small house in shape, and called a dooly. In short there are few plants which have such a variety of uses.
2nd.—This last summer is said by every one to have been remarkable for the quantity of seed produced by almost all plants; and acorns were particularly plentiful. Some were gathered for the purpose of sowing; but an immense number remained under the oak trees in the lawn, till within these few days, when they all disappeared, and what fell from the trees in the course of one day, had vanished before the next. After much puzzling about what could have become of them, Wentworth discovered that the sheep eat them; he caught them in the act to-day. He also observed that chaffinches and other birds eat beech-masts—but I do not wonder at that, for I think them excellent; and my aunt tells me that on some parts of the continent they are very much used as food by the poor inhabitants. The oil which is previously expressed from them is of the finest quality; and in Alsace, as well as all along the borders of France and Germany, the peasants make a sort of cake with the remainder.
I saw the jay to-day for the first time; Mary shewed me several of these pretty birds under a hedge. We watched them for some time, and I actually saw one raise and depress the bunch of black and white feathers on his forehead repeatedly; the wing coverts are beautiful. Jays are very affectionate to their young, who remain with their parents during all the autumn and winter months, instead of separating early, as most birds do. In winter they are to be seen continually under high hedges, or on the sunny side of woods and copses, seeking for acorns, crab-apples, or for the grubs and worms to be found in fields where cows have pastured. They are timid and watchful, and feed in silence; but timid as they are, they are very destructive in summer to the gardens.
The Lumleys, you know, live in a very sequestered part of the forest, and the jays seem to have established themselves in that undisturbed spot. Miss Lumley told me that they make great havoc among the beans in June; and though in general cautious and wary, at that season their boldness is quite remarkable, and nothing seems to intimidate them. She has frequently seen one of the parent birds descend from a tree into the bean rows—they soon announce their discovery by a low but particular scream, and then all the family hastened to join in the plunder.
Their throat is so wide that they can swallow beans, acorns, and even chesnuts whole; and it is said they can imitate various sounds, such as the bleating of a lamb, the hooting of an owl, the mewing of a cat, and even the neighing of a horse.