Page:Popular Science Monthly Volume 40.djvu/643

  as applied to schools and school children; but, in addition to these sanitary measures as applied to the mass, inspection of individual cases should be insisted upon. How many useful eyes might have been saved to the commonwealth if they had been examined and treated early in life by a competent oculist!

It is a rule—to which there are few exceptions—that, in addition to those defects which all eyes possess in common, the human organ of sight is, about the school age, prone to certain diseases, arising from inherent anomalies of structure, from heredity, from the results of infantile diseases, and from other causes. It is also true that many, if not most, of these dangers to which the eye in after-life is subject may be warded off by precautions suitable to individual cases. Thus the myope, or short-sighted person, should exercise care of a kind quite different from that which is suitable to the hyperope, or long-sighted individual; while the unfortunate astigmatic child (with "blurred" sight) should follow a prophylactic programme of a kind distinct from either; and so on through the list of possible ocular defects, which, although they commonly elude even the watchful eye of parent or guardian, are still possible sources of future disease. The advance of ophthalmological science has reached that point where one may read in the defective eyes of childhood the record of a large percentage of the impaired, restricted, or lost vision of later years.



THE DEVELOPMENT OF AMERICAN INDUSTRIES SINCE COLUMBUS. XIII.

HE organ is the most magnificent and comprehensive of all musical instruments. While the pipes of Pan—aside from that mythical personage—indicate a very ancient use of pipes as a means of producing musical sounds, the "water-organ of the ancients" furnishes to the student of organ history the first tangible clew regarding the remote evolution of the instrument. In the second century the magripha, an organ of ten pipes with a crude key-board, is said to have existed, but accounts of this instrument are involved in much obscurity. It is averred that an organ—the gift of Constantine—was in the possession of King Pepin of France in 757; but Aldhelm, a monk, makes mention of an organ with "gilt pipes" as far back as the year 700. Wolston speaks of an organ containing 400 pipes, which was erected in the tenth century in England. This instrument was blown by "thirteen separate pairs of bellows." It also contained a large 