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THE POPULAR SCIENCE MONTHLY. 



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 detect- 

 ed. 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 ob- 

 ject. 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 Gar- 

 dener's Monthly for August gives some in- 

 stances of anastomosis, or natural grafting 

 of plants, which came under his own obser- 

 vation. 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 phe- 

 nomenon 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, de- 

 scribes similar phenomena which he ob- 

 served 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 ex- 

 hibited 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 diffi- 

 cult 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 natu- 

 ral grafting ; but, in the case of roots under- 

 ground, such cause for union cannot operate. 

 In both these instances, it is worthy of re- 

 mark 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 na- 

 ture 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 cali- 

 saya, or yellow-bark, has fairly succeeded ; 

 but the succirubra, or red-bark, has pros- 

 pered beyond all expectation. There are 

 now 2,500 acres under succirubra. A mod- 

 erate 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 ap- 

 peared to be inevitable, as the cinchona- 

 trees were fast disappearing in South Amer- 

 ica. " 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 hap- 

 py homes, busy factories, and flourishing 

 colonies, in districts which, without this in- 

 valuable 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 



