Page:Popular Science Monthly Volume 11.djvu/522

506 as much impurity. "From data gathered by me," says Dr. Hunt, "and published some years since in a 'Report of the Geological Survey of Canada,' it appears that the amount of foreign matters in Turk's Island salt is 2.34; in Saginaw salt, 2.00; in Syracuse solar salt, 1.15; and in the boiled salt from the same locality about 1.50 per cent. Of the salt made at Goderich from the brines pumped from the salt-bearing strata of the region, three samples, analyzed by me in 1871, gave: for coarsely crystalline salt) 1.097; flaky medium salt, 1.282; and fine salt, 1.625 per cent, of foreign impurities. The fine salt, which is the least pure, is made by boiling, the others by slower evaporation. The analysis by Dr. Goessmann of another sample of Goderich boiled salt gave 1.50; while the rock-salt from the layer of 10 feet in Division VIII. of the section [the twenty-five-foot layer mentioned above] contains only 0.234 per cent., or less than one-sixth of the amount of foreign matter found in the boiled salt made from the Goderich brines."

About the English Sparrow.—A spirited but entirely courteous controversy is being carried on in the columns of our contemporary. Forest and Stream, about the English sparrow. The principal questions in dispute are whether this bird is useful as a destroyer of noxious insects, worms, and the like, and whether it banishes from its haunts all other species of small birds. The evidence is conflicting. Some of the writers say of the sparrows that they are "exceedingly quarrelsome among themselves," and intolerant of birds of a different species. When a stranger-bird makes his appearance among them, the fury of the whole sparrow community is turned upon him; they chase him hither and thither, giving him no rest until he is banished from the neighborhood. "They" (the sparrows) "let the orchards go to ruin," we are told, "for they will not eat every kind of insect." One writer sums up the case against the sparrows thus: 1. They have no personal attractions except their tameness; 2. They are practically useless; they may have been useful on their first arrival from Europe, but they are too much pampered to be so now; 3. They destroy fruit-blossoms; 4. They are often quarrelsome, and sometimes drive away useful birds. On the other hand, we are told that the sparrows destroy immense numbers of larvæ, especially during the winter; that they are not hostile to other birds; that they do not destroy fruit-germs. A writer who lives in Tenafly, New Jersey, says: "We have a few sparrows in the yard, and find their presence makes very little difference with the other birds. We have sixteen varieties of birds in the yard at this writing, viz., brown thrush, robins, catbirds, orioles, wood-robin, bluebirds, phoebe-bird, cuckoo, kingbird, and the rest warblers of different kinds. We find the most quarrelsome to be the kingbird and black oriole. These last are chasing almost everything that crosses their path."

Hygiene of the Eyes.—A series of questions touching the care of the eyes were recently submitted to Dr. E. G. Loring, Jr., by the Medico-Legal Society of New York. Dr. Loring replied in a paper which has since been published in the Medical Record. To the first question—namely, whether bad air has any direct effect on the sight?—the author replies that vitiated air has a specially irritating influence on the mucous membrane of the eye; and that bad air, as a primal cause, may set in train morbid processes which not only will affect the working capacity and integrity of the organ, but may even lead to its total destruction. The second question was, whether size and quality of type may cause disease of the eye? According to Dr. Loring, the smallest print which a normal eye can readily recognize at a distance of one foot is about inch, and at eighteen inches' distance about  inch. The normal eye should never be subjected for any length of time to a type smaller than twice this size, or inch, and it would be better, after middle-life, to employ a type even a little larger than this; but the employment of spectacles removes in a great degree the necessity of a larger type with advancing years. The finer the type, the closer the book has to be held to the eye, and the greater the demand on the focalizing power and the muscles that bring both eyes to bear at once upon the print. On the other hand, too coarse type is wearisome to the