Open main menu

Page:Popular Science Monthly Volume 24.djvu/424

This page has been validated.
410
THE POPULAR SCIENCE MONTHLY.

But, when Harvard is ready to remove Greek from the list of prescribed subjects, I believe that many classical schools will be found liberal enough to give pupils every opportunity to replace its study with German, mathematics, and science, taught by men both competent and sincere.

George F. Forbes,
Master in Roxbury Latin School.
Roxbury, Mass., November 14, 1883.
 

 

THE HOME-MADE TELESCOPE.

Messrs. Editors:

While reading the very useful article in the November issue of the "Monthly," by Dr. George Pyburn, on "A Home-made Telescope," it occurred to me that my own experience in that direction, not covered by Dr. Pyburn's article, might prove acceptable to some of your readers. In constructing my telescope I made the tube of paper and paste substantially as described by Dr. Pyburn, finishing with shellac-varnish as a protection against moisture. The three-inch object-glass cost about twenty-five dollars, which is nearly the total outlay for the instrument, as I use for eye-pieces those belonging to my microscope. As these range from a two-inch to a four-inch, I get a fair astronomical telescope with powers from twenty-five to two hundred diameters, affording satisfactory views of the more interesting celestial objects. For viewing the sun, a light box open on one side is attached to the tube, containing a sheet of white paper on which the image of the sun is received at a distance of nine or ten inches from the eye-piece. The stand is unskillfully constructed of wood, but, as the instrument is supported at two points, it is steady. It is of convenient height for an observer in a sitting posture, the object-end of the telescope being made to swing. When in use the telescope is strapped in a kind of long trough made by nailing two strips of boards together. This support is bolted at the end next the observer to an axle having a vertical motion. It has a horizontal motion on the bolt. The end of the support toward the object is given a vertical motion from horizontal to perpendicular by a lever running through a mortice in the stand, and working on a pin in the mortice. A rod jointed on the lower end of the lever is always in reach of the observer with which to manipulate it. The top of the lever is fitted with a long horizontal roller, on which a roller placed under the telescope-support rests at right angles. The rollers crossing each other at right angles, smooth and steady motion is had both vertically and horizontally. Such a stand may be made in a day.

George W. Morehouse.
Wayland, New York, October 29, 1883.
 

 

INSECTS AS CARRIERS OF DISEASE.

Messrs. Editors:

Although not prepared to accept entirely the theory so ably presented by Dr. King, in the September number of your magazine, as to the mosquital origin of malaria, I believe in the power of insects to transmit and disseminate infectious diseases. The active agency of mosquitoes and other insects in the spread of yellow fever has never been fully appreciated, and it is to be hoped that the attention of the boards of health in the localities liable to this terrible scourge will be directed to this source of danger, and that they will establish cordons of fires as well as men around infected districts. However, my object in writing this is merely to add further testimony as to the fact of insects carrying disease.

The interior counties of the Southern States are infested by a minute fly, a little larger than the sand-fly of the coast, but without the sting of the latter. They are called gnats or black gnats, and are exceedingly troublesome, from their habit of flying into the ears and eyes of both men and animals. They also gather upon any running sore or abrasion of the skin, and, though they do not bite or sting, they are very irritating. When they get into the eye they cause a very sharp pain, and, though immediately killed by the secretions, the eye feels the effects for some hours after. It has been observed that during the seasons when these gnats are most plentiful the disease known as sore-eyes is most common and severe.

Not being a physician, I do not know the name of the disease, but it is very contagious, and usually affects an entire family when once introduced into it. The lids of the eye become irritated and swollen, and the entire ball is red and inflamed. Some persons have lost the sight of one or both eyes from it, and its effects are felt for months after recovery. The intimate relation existing between this disease and the gnats is so well recognized that the negroes say it is caused by the gnats laying their eggs in the eye. This, of course, is improbable, but points clearly to them as the real cause in some way. I do not think the irritation arising from their getting into the eye is the origin of the trouble, because the disease does not always or even generally follow as a matter of course; but I do think that the germs are carried upon the legs or wings of the gnats, and that, when one so charged touches or gets into the eye, the germ or bacteria is deposited, and from that the disease is developed.

Of course, there are other ways of transmitting the disease, but the most active agent is undoubtedly the gnat, since after it disappears the disease ceases to spread, and gradually loses its character as an epi