Democratic Sentinel, Volume 17, Number 28, Rensselaer, Jasper County, 4 August 1893 — POPULAR SCIENCE NOTES. [ARTICLE]

POPULAR SCIENCE NOTES.

A Portablr Electric Fan.—Thoelectric fan has come to be such an indispensable element of comfort, if not of existence, during the summer months that new and Improved forms are constantly making their appearance. One of these adds the very decided recommendation of economy to that of efficiency. Its first cost, with battery complete, is small, and the cost of operating it afterward is nut at two and threequarter cents an hour. It is claimed that the battery will last ten weeks without, renewal at one hour’s work daily, or tew days at a steady operation of seven and ahalf hours per diem. It is designed tob« suitable for the parlor or dining table, being both ornamental and noiseless. It will not drop grease on tho tablecloth or carpets, for its bearings are self-oiling, and carry on their own lubrication without loss of the lubricant. The whole outfit packs up in a small box, and can. be carried without inconvenience. Electric Car Heating. —Said a lecturer in Chicago recently: The electric railway opened up the field for electric heating. Reports from roads operating in Northern Miohigan and in other portions of the United States and Canada, where the winters are unusually cold,, ■how that from 1,200 to 1,500 watts issufficient current to keep the average sixteen-foot car warm in all kinds of weather. It will be seen that, inasmuch, as the heaters require no attention whatever, and aro practicnlly a fixture of the car, the cost of maintaining and operating on the average electric road will be simply the cost of current. Coal stoves take from twenty to forty cents per day. to operate, if the least account is taken, of timo used to keep them in heating condition. The coal stove also' takos up room for one or more passengers while it remains in the car, which, on a road doing a good business, is a. very important item. Coal stoves, too; on cold days, when being heated unusually warm, become so hot that it is often im|K)Bsiblc to stand immediately in> front of tho stove without burning the clothing of the person stauding near:. The oleetric heatera, being plncod under the seats out of the way and furnishing a lower temperature, oannot be objected to on this score, and being entirely out of the way of passengers and taking up no space iu the car which can be utilised tobring in a dividend, often saves in a day more than the entire cost of the current furnished them for the day’s run. Thera aro many times in tho spring and falL whon the mornings and evenings arecool and the middle of the day warm, whon u heated car for a few hours each day would add greatly to the comfort of passengers. With coal stoves this is. often impossible, unless tho car can be taken out of service long enough to huva a lire rebuilt in tho stove. CURVATURE OK THIS EARTH'S SURFACE. —Generally speaking, we say that the curvature of tho earth amounts to aboutseven inches to the statute mile; it is exaotly tl.oo inches or 7.0(52 Inches for a geographical mile. The effect of the known eurvuturo of our globe may be illustrated in the following manner: Take down your globe, place a book,, pane of glass or even a ruler against it, either of the two objects first named being best adapted to such an experiment. You will observe instantly that the book,, pane or ruler only touches the miniature representation of tho earth at one point, tho globe's surface falling away in all directions from the point of contact. Now, suppose tho ocean’s surface was culm and fro/.en and a sheet of glass many miles square laid upon it. At one mile from the place of contact the glass would stand out nearly eight inches (this mcneurement upon the ocean, the utile is a nautical one)—in fact, will lack but 38-IOOtX' of an inch of being eight inches trom the pane; at three miles it will be six feet, and at nine miles fifty-four feet, and so on according to the regular ratio. In. order to get the whole matter iu a nutshell remember that the number of feet of depression is equal to two-thirds of tho square of the number of miles for any observable distance. There is, however, an error resulting from refraction which must be cancelled. The commonly used formula for correction is as follows: square the number of miles and take-four-soveuths of it for the correction in feet. Thus, if an object is visible at a distance of five miles we may know that its height is at least 14} feet. Or,, it the height of a visibio object is known - -suy 100 feet—take one-fourth of that number,or 25, multiply by seven and take the square root of the product and you will have the distance of the object, which ia iu this cuso a fraction over miles, A man swimming in the ocean, may see a tower 19 miles away, even, though it only be 200 feet high, but now elevate that man 100 ffeot above tho suriaco of the water and he could plainly see a tower only 100 feet high, even though it be 26 milea. away.