2 Proceedings of the Royal Society of Victoria. 



Arrangements. 



The pendulums and svibsidiaty apparatus* were carefully 

 packed at the Melboui'ne Observatory and shipped to Sydney, 

 whither I proceeded on 19th January. Mr. Russell, the Govern- 

 ment Astronomer at Sydney, had very kindly placed at my 

 disposal the cellar in which the experiments of the U.S. Coast 

 Survey party, and subsequently those of Lieutenant Elblein, had 

 been cai-ried out ; and as the exact position of their apparatus in 

 the cellar is known I erected mine on the same spot. The cellar 

 itself is almost an ideal room for the purpose. Three of the walls 

 are of brick ; one, which is two feet ten inches thick, is directly 

 in contact with the earth outside, forming part of the foundation 

 wall of the Observatory ; the other two, which are two feet four 

 inches thick, form partition walls separating the room from 

 adjoining cellars, as does also the fourtli wall, which is a mass of 

 stone four feet three inches thick, and supports the Transit 

 instrument. At either end of the Transit wall are narrow 

 passages communicating with the adjoining cellar. The ceiling, 

 which is of wooden panels, is level with the ground outside. 

 There are no windows ; but at the east end — remote from the 

 pendulum apparatus — a staircase leads up into the Transit room. 

 The dimensions of the cellar are twenty-four feet by six feet five 

 inches by seven feet seven inches. As might be expected from 

 this description the diurnal variation of tempei'ature cannot" be 

 detected in this room, even by experiments specially carried out 

 for the purpose.! 



The floor, on which the pendulum stand was erected, consists 

 of six inches of concrete resting directly on a bed of vei-y hard 

 clay containing a large number of iron stone nodules. This clay 

 bed, which is nearly one foot thick, is in its undisturbed natural 

 ■condition and very solid ; it rests directly on the Sydney sand- 

 stone. A method of testing the stability of the apparatus — and 

 of the floor too — is given in the Appendix. 



• Described in the Report of the Gravity Survey Committee for 1892— Proc. Roy. Soc. 

 Vic, 1892, p. 219, 



1 1 kept the tbennographs running whetlier I were at work or not ; on certain days no 

 one entered tlie cellar, and the records for those days are straight lines. A range in 

 temperature of 0'1° Fahr. could he detectel at once by the wave it would produce iu the 

 line ; but none such was found. 



