416 Intelligence and Miscellaneous Articles. 



telescope was attached to the wire beneath. I thought to have per- 

 ceived thereon the daily alternation of forward and backward mo- 

 tion of the earth's surface in relation to the earth's motion in its 

 orbit, and so also with all certainty very distant earthquakes, &c. 

 I wish that some one may find an opportunity to make these obser- 

 vations in a pit, with due accuracy. Reichenbach has proposed for 

 it a very large level [compare A. "Wagner's observations of earth- 

 quakes in South Europe on the level of the large transit-instrument 

 at Pulkowa]; and I believe that the swing balance made by one of 

 my pupils (of the name of Engeller), adapted on a large scale might, 

 as a preliminary arrangement do excellent service : — 



O 



" It consists of a horizontal lever a b of brass, on which is fixed 

 at one end a brass ball c as a weight ; cl is a fine wire, by which the 

 lever is suspended ; instead of the counterpoise, the other arm of 

 the lever is fastened to the floor by the wire e ; and the instrument 

 becomes the more delicate the nearer the wire d comes to the wire e. 

 The ball c can oscillate only horizontally, and is visibly (according 

 to Hengeller's experiments) attracted by a cannon-ball. It would 

 be very meritorious to institute observations on this instrument. — Gr." 



This is therefore Zollner's horizontal pendulum complete, scale- 

 reading by telescope and all, though perhaps not with reading-off 

 by mirror ; and after the above statements there is certainly no 

 doubt that M. Zollner's bold idea, of demonstrating the variations 

 of the gravity of the earth and of cosmic attractions by terrestrial 

 observations at one and the same place, had already in 1817, there- 

 fore full 52 years previously, been expressed and proved experi- 

 mentally by Grruithiiisen in Munich — and further that the horizontal 

 pendulum, proposed for this purpose by Zollner, had been con- 

 structed and put to the test of experiment, at the latest, in 1832, 

 thus at least 37 years before Zollner, by a Munich student, a pupil 

 of Grruithuisen, of the name of Hengeller, although unfortunately 

 nothing further about the observations is communicated than that 

 they proved the usefulness of the instrument for the end proposed. 

 Thus, then, this important thought, like so many similar, did not 

 come to light at once and complete, but emerged in a less perfect 

 form a long time previously in isolated original minds, and, because 

 the time was not ripe for it, passed away unnoticed. Hengeller 

 must have been a genius ; and since he studied between 1828 and 

 1832 at Munich, where Gruithuisen was Professor, it might per- 

 haps still be possible to learn something more about his personality. 

 — Sitzung der math.-naturw. Classe der Tc. bohmischen Gesellsch. d. 

 Wissenschaften, November 15, 1872. 



