Popular Science Monthly 



827 



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. 



