KNo\VLi:nr,i:. 



August, 1912. 



It is uvicii-nt, tlicrcfori-. that, at tlic lust, tin- 

 doctrine of thi; indcstructil)ility of matter is a 

 pure hypotlusis, entirely unsupported hy scientific 

 evidence : indeed, so far as we can see, contradicted 

 thereby. This fact is very generally recognised hy 

 physicists no\v-a-days*, hut many people still 

 helicve that the doctrine of the indestru<til)ility of 

 matter is a law of the highest scientific importance, 

 snpi)orted hy the most convincing evidence. It 

 is nothing of the sort. The e.xpression " law of the 



indestructil'ility nf matter" does figure largely in old 

 scientific text-hooks, but it is quite a mistake to 

 sujjpose that this so-called "law" is one of the 

 foundation-stones of modern science. The law of the 

 conservation of inertia, which is true under all but the 

 most exceptional conditions, and which is a general- 

 ised statement of observed facts involving nothing 

 hypothetical, suffices for all the purjjoses of the natural 

 sciences for which the hypothetical " law of the 

 indestructibility of matter" was at one time em|)loyed. 



Cf. Professor II. C. Jones, "The ICIcinciits of I'hysic.il Chemistry" 11902), p. 2. 



l<:\■I•K^■M.\^"s astronomy 



i;v 1)K. AIJ Kill) GK.\Di;X\VITZ. 



MdKK and more attention is paid to astronomical instruction in 

 the curricuUun of grammar schools, and some German 

 "Gymnasia" have even gone so far as to install observatories 

 of their own. As, on the other hand, the number of amateur 

 astronomers is rapidly increasing, there is obviously a need for 

 designing special instruments for lay people which, while 

 warranting a suflicient degree of accuracy, may enable any- 



I'lGlKK J J 6. 

 The New Star Finder. 



body without m.athcmatical calculation to get a clear insight 

 into the topography of the heavens. 



A German instrument maker, F. Sartorius, of Gbttingen, has 

 designed a " star finder." an astronomical instrument of sur- 

 prising simplicity and remarkable precision, which enables any 

 layman to ascertain the name of any star observed in the sky 

 and the constellation to which it belongs or, inversely, to find 

 out any given star from its name and position. Its design is 

 based on the following considerations : 



The position of a star in the sky is known to be defined by 

 two angles, viz., rectascension and declination, corresponding 

 to the geographical longtitude and latitude respectively of 

 points on the globe. .Again, orientation in the sky. the same 

 as on the earth, should be based on the North-South direction 

 of the magnetic needle. This is why the star-finder primarily 

 comprises a compass. 



The star-map which forms an indispensable part of any 

 instrument of this kind, should be adjustable parallel to the 

 equator which serves as basis in determining the latitude and 

 longitude. The horizontal position of the axis round which 

 the star map is free to rotate, therefore, is ascertained by a 

 level, and a graduated circle allows the map to be adjusted to 

 the geographical latitude of any given locality. Now, all stars 

 and constellations in their apparent twenty-four hours' revolu- 

 tion, due to the rotation of the earth, are known to advance 

 each hour an always constant distance, their angle with regard 

 to the initial meridian changing progressively. On the other 

 hand, on account of the revolution of the Earth round the Sun, 

 the point of the sky which at noon or at midnight occupies 

 the highest position or passes through the meridian, advances 

 about one degree (360 365) in a western direction: that is to 

 say that the stars in their turn perform a progressive motion 

 from East to West. 



These principles are utilized so cleverly in the star-finder 

 that a few manipulations, without any mathematical calcula- 

 tion, suffice to find out any star desired. 



Koinid the centre of the star-map there are free to turn two 

 rectangular arms, one of which carries at its end the graduated 

 declination circle. On this circle rotates a diopter, which is 

 pointed towards the star and which by its position on the 

 graduated circle, immediately indicates the declination of the 

 former. The rectangular arm carries, at right angles to the 

 diopter axle, a disc, which in its turn, on the inside hours' 

 graduation of the star-map, indicates the rectascension of the 

 star. The graduation of this disc agrees with that of the 

 declination circle, so that the star towards which the instru- 

 ment is pointed is read directly below the division of the 

 graduated disc marked by the diopter on the declination disc. 



The inside hours' graduation is surrounded by another dial 

 (diurnal and monthly), which in its turn is adjusted with regard 

 to the fixed outside hours' graduation. This allows the star- 

 map to follow the apparent progression of stars, the hourly 

 advance being continually accounted for. 



