Pendulum Apparatus. 91 



equation of each. The artificial star, which was made to 

 transit alternately from right and left, was contrived by 

 bringing a minute pencil of light to a focus in the place of 

 the wires of one of the collimating telescopes of the transit 

 instrument. 



Mr. Elleiy stated that the apparatus had not been brought 

 thoroughly into use yet, but from a few trials he hoped it 

 would be found to be a very easy and accurate method of 

 making this somewhat troublesome determination. He pro- 

 mised at some future time to communicate the result of his 

 experience with this apparatus. 



Art. XXIV. — Description of a Pendulum Apparatus for 

 Determining the Length of a Second-s Pendulum in 

 Melbourne. By Professor Neumayer 



[Abstract of paper read 31st August, 1863.] 



This paper was illustrated by some large drawings which 

 thoroughly explained the peculiarity of the pendulum used 

 by Professor Neumayer, as compared with Bessel's, Captain 

 Katers, &c. 



The pendulum itself was constructed by Mr. Lohmeir, of 

 Hamburg, under the supervision of Professor Peters, of the 

 Altona Observatory. It was reversible by two knife edges, 

 and was adjusted with such nicety that there remained a 

 difference of only 0-00024 of a second between the duration 

 of an oscillation in both positions of the pendulum. The 

 measuring apparatus consisted of a frame with two micro- 

 meter miscroscopes, in which either the pendulum or a scale 

 (a copy of Bessel's Prussian Standard) could be suspended, 

 and the knife edges in one case or the divisions of the scale 

 in the other brought under the micrometers. This apparatus 

 was constructed, under Professor Neumayer's own super- 

 vision, by Mr. H. Schreiber, of Melbourne. The micrometer 

 was capable of measuring to 0-0017 of an English inch, 

 The whole apparatus was conveniently fitted up in a 

 cellar under Professor Neumayer's house. The clock used 

 was one by Shepherd, of London, and was comparable 

 by means of a telegraphic needle connected by a wire 

 with the standard clock of the Melbourne Observatory, 

 about 500 yards distant. Comparisons were generally 

 made three times a day. The coincidences were 



