Page:Popular Science Monthly Volume 88.djvu/855

 Popular Science Monthly

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��iancy of each component exceeding the sun at least twenty fold, so that the total light of the system is equal to about five thousand suns! Imagine the condi- tions of the earth if we had such a pair of bodies to govern us.

In spite of their enormous size, the bodies are not so very massive, exceeding the sun only about twenty-five times in weight, and therefore they are much less dense than the sun, one hundred and fifty times smaller in density, which amounts to saying that they average about six times as hea\^ as the same volume of air. According to current theories of the life histor>^ of stars, Delta Orionis, like the other objects in Orion, is very young, and in due course of time will contract and cool off and become much more like the sun, though of course remaining more massive.

The case here selected illustrates what can be revealed by electrical measure- ments of light changes which have en- tirely escaped eye observation. Many other stars are being studied in the same way, and it is possible to measure their diameters and weigh them, when the only effect at the end of the telescope is a minute electrical current set up by the light action. Thus we see that astronomers are making use of the mod- ern technical advances, and in some cases, like the present, a new device may even be used with success in pure science before it is perfected for commerical purposes.

��Measuring Cloth in the Roll

THE inconvenience of unwinding a roll of cloth to measure it has been obviated by a clever mechanism de- vised by Anthony Fobare. The exact length of any roll of fabric can be ascer- tained in a few minutes.

The idea consists in passing a thread between the folds of the roll and measur- ing the thread. For this purpose a tool shown in Fig. i is used. The thread passes through a handle 2, which termi- nates in a projection 3 about the size of a large knitting-needle. A disk 4 is placed between the handle and the projection. When inserting the projection between the folds of cloth this guard presses against the end of the roll, keeping the

���Unwinding a roll of cloth is unnecessary to

find its length. A thread can be inserted

between the folds and the length of the

thread taken

��projection a uniform distance from the edge.

The spool is mounted on a box 16 (Fig. 2). The thread is held under tension by passing between two disks 23 held together by a spring. After passing around a large pulley 39 at- tached to the side of the box, the thread again passes through two tension-plates 43 and then into the handle of the threading-tool.

The circumference of the pulley 39 is just one yard. On the threaded shaft of this pulley is suspended a traveler or rider 34, which mo\es along the threads as the pulley is rotated. A pointer 38 indicates the number of turns on a scale 36, placed parallel to the shaft. Every turn stands for one yard. The inches are recorded on the face of the pulley, the circumference of which is divided into thirty-six parts. When the meas- urement is begun the pointer 42 and the rider 34 should both be at zero. The iniwinding of the thread, as it is woven into the roll of fabric, is thus recor«^ed in yards and inches.

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