Page:Popular Science Monthly Volume 16.djvu/151

 and you have for result a distance relatively very small; but divide by 8,000 the enormous number of leagues which represents the distance of a star, and there still remain a number of leagues too great to permit of the stars being seen by us in a perceptible form. In considering Jupiter, or any of the planets, we are filled with wonder at the thought that this little luminous point might hide not only all the visible stars, but a number 5,000 fold greater—for of stars visible to our eyes there are only about 5,000. All the stars of these many constellations, as the Great Bear, Cassiopeia, Orion, Andromeda, all the stars of the zodiac, even all the stars which are visible only from the earth's southern hemisphere, might be set in one plane, side by side, with no one overlapping another, even without the slightest contact between star and star, and yet they would occupy so small a space that, were it to be multiplied 5,000 fold, that space would be entirely covered by the disk of Jupiter, albeit that disk to us seems to be an inappreciable point."

A Scientific Detective.—One of the most remarkable among recent inventions is the induction-currents balance, briefly described as follows in the "Athenæum": "It consists of two induced currents from separate induction coils, which are so equal that they neutralize each other. They are connected with three elements of a Daniell'a battery, with a small clock and microphone, and a receiving telephone. If a piece of metal is placed in one of the coils, the balance of the currents is disturbed, and the clock is heard to tick; but if another piece of metal, exactly similar, is placed in the opposite coil, the balance is restored, and silence again prevails." From this brief description it will be understood that in this I new instrument the physicist has an exquisitely sensitive test of the molecular constitution of many substances, for it detects the presence of mixtures and alloys, however small the quantity. Hence a scale of qualities may be formed; and if the value of silver be placed at 115° there can be no question that everything that marks 115° must be silver, 52° will be iron, 40° lead, and 10° bismuth; and, further, the instrument is at once affected by magnetism, heat, or strain in the substance under examination, and will indicate even the effect of half a minute's rubbing of a piece of metal between the thumb and finger. The induction-currents balance is a contrivance of Professor Hughes's.

Stained Windows.—The method of constructing stained-glass windows is described as follows in "Chambers's Journal": "The design of the window being determined upon, and the cartoon or full-sized drawing being prepared, a kind of skeleton drawing is made showing only the lines which indicate the shape of each separate piece of glass. It is apparently not generally understood that a window is not one piece of glass, to which are applied the various colors displayed, but a number of small pieces, which are united by grooved lead, which incloses each individual fragment, and that each different color we see is the color of that particular piece of glass, the only painting material employed being the dark-brown pigment used to define the more delicate and minute details. This skeleton or working drawing then passes to the cutting-room, where sheets of glass of every imaginable shade are arranged in racks, each bearing a number, by which a particular tint is known. The drawing being numbered on each separate piece of glass by means of a frame containing small pieces of every shade, and each numbered according to the rack containing the glass of that color, the use of this frame renders unnecessary the tedious process of visiting each rack in search of the particular shade required; the glass is laid bit by bit on the drawing, and each piece is then cut to the required shape by means of a diamond. After the glass is cut, it passes to the painter, who, laying it over the drawing, traces upon it with his brush all the details of features, folds of drapery, foliage, etc., as designed by the artist. But as the action of the weather and the continually varying conditions of the atmosphere would speedily remove every vestige of paint if left in this state, it is necessary to subject the painted glass to the action of heat by placing it for several hours in a kiln, under the influence of which the paint is fused into absolute affinity with the glass, and