214 



SCIENCE 



[N. S. Vol. L. No. 1287 



ista veneziano del see. XVIII."; Ant. Favaro, 

 " Matteo Carosio (Amici e eorrispondenti di 

 G-alileo. XLI.)"; Gino Loria, "Per una storia 

 della matematica nel secolo XIX."; Andrea 

 Oorsini, " L" influenza ' oggi e nel passato " ; 

 Studi 6 ISTote Vinciane Proemio, D. T. Per 

 I'edizione nazionale delle opere di Leonardo, 

 Notizie varie; Bibliografia metodica dei lavori 

 di storia della seienza publicati in Italia; 

 Analisi critiche: E. Ahnagia, Cristoforo 

 Colombo (G. Stefanini) ; U. Viviana, Andrea 

 Cesalpino; E. Mareolongo, II problema dei 

 tre corpi; W. Libby, An Introduction to tbe 

 History of Science (A. Mieli) ; Gli Scienziati 

 Italiani, Aggiunte, note e discussiono ; Notizie 

 e Commenti : Organizzazioni italiane per pro- 

 muovere lo studio della storia della seienza 

 (A. Mieli). La storia della seienza nolle Uni- 

 versita — N'otizie varie. 



Due credit, must be given, even to-day, to 

 the Germans for their activity in the publi- 

 cation of journals of an international char- 

 acter. However, Americans should now realize 

 the desirability of stimulating and encour- 

 aging Italian, English and other European 

 scientific publications of an international 

 character. The revived Belgian journal Isis^ 

 now published by Dr. George Sarton and Dr. 

 Charles Singer, of Oxford, should be remem- 

 bered in this connection. 



The best way to stimulate these publica- 

 tions is by personal subscription and by per- 

 sonal interest on the part of scientists in 

 urging upon librarians the subscription to 

 these enterprises. 



Louis C. Kaepinski 



XJNiVEESirT OP Michigan 



SPECIAL ARTICLES 



THE MOTION OF A GRAVITATING NEEDLE' 



1. Static Elongations. — The apparatus^ with 

 which I am working is of the simplest char- 

 acter, but judiciously designed. Two shots 

 (m = .6 gram), one at each end of a straw 

 shaft 22 cm. long (diagram la), are sup- 

 ported by a long quartz fiber, fi^sed with 



1 Advance note from a Report to the Carnegie 

 Institution of Washington, D. 0. 



2 Proc. Nat. Ac. Sc, IV., 338, 1918.' 



cement above and below. The attracting 

 weight (M ^1 kilog., or more) can easily be 

 moved from one side to the other and defi- 

 nitely placed by a smooth-working crank 

 mechanism, between stops. Observations are 

 made in a dark room (except for distant lamp 

 light), in a damp, semi-subterranean basement, 

 in midsummer, with very fair constancy of 

 temperature and no electric charges. The 

 motion of the needle is essentially creeping 

 with a period (if I may so call it) of 20 or 30 

 minutes. The scale distance is over 4 meters 

 from the little mirror at the center of the 

 shaft. The observer keeps out of the way. 



Under these circumstances reasonably con- 

 stant scale deflections, for periods of alterna- 

 tion exceeding 30 minutes would be expected; 

 but the reverse of the ease. Here is an ex- 

 ample of the successive mean excursions or 

 double amplitudes of thevneedle during the 

 day: :' 



July 16 17 18 19 20 



Scale displacement 



in em 2.79 3.02 3.27 2.79 3.65 



July 21 22 23 25 25 



Scale displacement 



in em 4.03 3.64 3.07 4.50 5.39 



The values of the morning and afternoon 

 readings were equally diilerent. Individual 

 excursions may run as high as 6 cm. on cer- 

 tain days, though the behavior is throughout, 

 of course, quite systematic. 



2. Triplets for three-minute Periods.- — The 

 results for short period alternations of the pull 

 of M (3 minutes in the examples given. Figs. 

 1, 2, 3) are equally bizarre; though, here they 

 become interesting. In Fig. 1, the turning 

 points of M are indicated by little circles, 

 B and L are pulls to right and to left, respec- 

 tively, and the mean double amplitude of the 

 successive triplets are marked on the curves. 

 There is drift throughout the figure; other- 

 wise the behavior is about what wotdd be ex- 

 pected. Inertia apparently carries the ball a 

 little time after the gravitational pull has 

 changed sign. But for this, there would be a 

 phase difference of 90° as there should be. 

 Moreover, the motion of the needle, after 

 turning, is uniform. 



