cles with which to read. Instances are cited of persons who, while employing both eyes for ordinary vision, usually employ only one in reading. If any difference of the kind exists between the visual powers of a pair of eyes, it may be readily detected. Hold up a piece of card before one eye, so as to cut off its field of view, and then look at some object before you with the other. Then gradually bring the card before the other eye, and view the same object. If the object is seen with the same distinctness in each case, then your eyes are perfect as regards the balance of their foci: if not, then there is focal difference more or less decided. It would no doubt be advisable to take account of this very frequent difference of focus, in selecting a pair of spectacles.
Natural Grafting.—A writer in the Gardener's Monthly for August gives some instances of anastomosis, or natural grafting of plants, which came under his own observation. In The Popular Science Monthly for March, 1873, we gave Goeppert's theory, accounting for the continued life and growth, in some cases, of the stumps of pine and fir trees. Goeppert's explanation of the phenomenon is, that the roots of these stumps are nourished with sap derived from the roots of trees in their neighborhood, with which they are in contact. Such roots are found deeply embedded in one another, and so consolidated as to become practically continuous. The writer in the Gardener's Monthly, after briefly stating these facts, describes similar phenomena which he observed last spring among the branches of two apple-trees.
In one of these the limbs so crowded one another that it was resolved to cut one away. It was accordingly sawed off; but still it did not fall. It was then found that the dismembered branch was firmly united to a limb situated beneath it. With a hatchet the writer then cut it near the point of union; but the end of the branch still lives and thrives, bearing blossoms and fruit in season. Another tree was found, but a few yards distant from the first, which exhibited the same phenomenon of natural grafting. "I had never before," continues the writer, "seen or heard of such a case in an apple-tree, but I do not think it so difficult to account for as the condition of the coniferous trees. It is natural to suppose that the motion of the wind may occasion abrasion of the bark on the limbs of apple-trees, and thus prepare them for this natural grafting; but, in the case of roots underground, such cause for union cannot operate. In both these instances, it is worthy of remark that the trees were of the kind called American Pippin, or Grindstone." But surely there is no difficulty in conceiving of two roots from different trees growing into contact, when compressed together into a narrow space owing to the refractory nature of the soil. Under such circumstances they might rub away each other's bark at the point of contact, and establish between themselves such an exchange of living force as would constitute a life in common.
The Quinine-Supply.—The cultivation of the cinchona-tree in India, which was commenced in 1860, is making satisfactory progress. Near Darjeeling are two large plantations, one owned by the government, and the other by an association. The three principal varieties of the cinchona, officinalis, calisaya, and succirubra, were all planted at Darjeeling, with a view to find which variety would thrive best there. The officinalis, or gray-bark variety, failed utterly; the calisaya, or yellow-bark, has fairly succeeded; but the succirubra, or red-bark, has prospered beyond all expectation. There are now 2,500 acres under succirubra. A moderate estimate gives the produce of these plantations for the next three years at 200,000 lbs., calculated to produce 6,000 lbs. of quinine, and an equal amount of other valuable alkaloids.
Some years since a quinine famine appeared to be inevitable, as the cinchona-trees were fast disappearing in South America. "The drug," writes Berthold Seemann, "is almost as indispensable to mankind as air itself, and, aided by this silent agent, Europeans have been able to establish happy homes, busy factories, and flourishing colonies, in districts which, without this invaluable aid, would have simply become their graveyards. Our only wonder is, how we could ever have done without it, and what would become of us if the supply
