Page:Popular Science Monthly Volume 11.djvu/523

Rh eye, requiring more exertion of the muscles that govern the movements of the eye. The distance between the lines should be about one-eighth inch; nearer than this is apt to be confusing, farther apart is also confusing. Heavy-faced type is preferable to lightface. An almost imperceptible yellow tint in the paper, "natural tint," is very desirable; pure white paper, especially if it has a metallic lustre with bluish tinge, should not be employed. The paper should be thick enough not to be transparent, should have a close, fine texture, and be free from sponginess. To the third question—whether too long and constrained attention to one object, without rest or variety, will cause eye disease?—Dr. Loring replies affirmatively, and assigns the physiological reasons. Finally, he was asked whether the angle at which light strikes the eye is important? He replies that the light should not come directly in front; neither should it come from directly behind. It should not come from the right side, because, in writing, the shadow of the hand falls across the page; and a moving shadow over a lighted surface not only reduces the quantity of light and leads to a stooping position, but it is also more annoying to the eye than a uniform reduction in the illumination of even a greater degree. The best direction for the light to come is from the left-hand side, and from rather above than below the level of the hand.

High Temperatures and Bowel-Complaints.—Dr. N. S. Davis, in a "Report on Clinical and Meteorological Records" communicated to the American Medical Association, an abstract of which we find in the Medical Record, reaches the conclusion that the bowel affections, so characteristic of this temperate climate, begin invariably with the first week of continuous high temperature, and that every subsequent occurrence of several days and nights of continuous high temperature causes new attacks to be increased in number throughout the month of July, less in August, and still less in September; that it is not simply the extreme of heat, but its duration, which determines the number of attacks; that this continuous high heat, to be efficient in producing these affections, must follow a protracted season of cold; and that, if we compare these deductions directly with statistics of mortality, we shall find them to conform in every particular in that the high rate of mortality follows exactly the same line. That fact was regarded as one of great importance in connection with sanitary measures which were to be adopted for the protection of life in infants; preventive measures must strike with the first week of consecutive high temperature. These conclusions were corroborated by quotations from mortality-tables.

Manurial Value of Spent Tan and Sawdust.—From careful analyses of spent tans and dyewoods and other similar waste materials. Prof. F. H. Storer, of the Bussy Institution, reaches the general conclusion that they contain but a very small proportion of fertilizing substances, and that practically, whether they be fresh or rotten, they have very little value as manure. Of fresh sawdust, even that from hard woods, he says that it can hardly be considered an economical manure; it is far inferior, for compost, to peat. But, curiously enough, the chemical evidence goes to show that it is for feeding animals rather than for feeding plants that sawdust might be put to use. Fresh sawdust, even that of pine trees, can be used with advantage as fodder in times of dearth. Twigs and leaves, as the clippings of vines and hedges, or bushes mown in pastures, are undoubtedly valuable both as manure and forage. Autumn leaves and the rakings of woodland, which consist for the most part of leaves that have not only fallen, but have been bleached by rains, may be classed as somewhat inferior to straw.

Wearing Qualities of Aluminium.—The comparative resistance of aluminium to change of color and wear, when brought into daily use, has been made the subject of observation by Dr. C. Winkler, of Freiberg, who finds, according to the Polytechnic Review, that it is inferior to silver in retaining color and lustre, being about on a par with German-silver in these respects; while it wears away more rapidly than silver, but less so than German-silver. Spoons made of all three materials, each having exactly the