Observations zvith Kater's Pendulums. 175 



This table (No. IV.) embodies the conclusion of the diiierential 

 results. It will be seen that by diminishing the vibration 

 number of Pendulum No. 6, and by increasing the vibration 

 number of Pendulum No. 11 by (say) 0-5 vibrations in the 

 column for Kevv, the columns containing the differences would 

 be brought into much closer adjustment. If comparisons of 

 several clocks are involved in the operations, errors of O"-") 

 vibrations could be very easily introduced. 



For the conversion of the differential results into absolute 

 measure of the force of Gravity for Melbourne, we have now the 

 Greenwich, Kew, and Vienna bases, and Professor Neumayer's 

 independent value of ,4f. 



The absolute length of the seconds pendulum at Greenwich, was 

 determined by General Sabine in 1830, by the convertible pendulum 

 originally designed and employed by Captain Kater in 1817, and 

 found to be 39-13734 inches. (See Phil. Trans., 1831, Art. xxv). 

 In 1873 Major Heaviside determined the length of the pendu- 

 lum vibrating seconds at Kew, using the same pendulum as that 

 used by General Sabine at Greenwich ; its length was remeasured 

 by Colonel Clarke. As the result of these observations, the length 

 of the seconds pendulum at Kew was determined to be 

 39-14008 inches, and this result was corroborated by the 

 operations with the two reversible Russian pendulums at Kew, 

 but these pendulums do not seem to have given satisfactory 

 results elsewhere (as shown in the volume v. of The Great 

 Trigo7iometrical Survey of Itidia). 



Professor Neumayer determined the value of g at Melbourne in 

 1863, by a reversible pendulum constructed by Mr. Lohmeir of 

 Hamburg, under the supervision of Professor Peters of the Altona 

 Observatory. Of these operations no detailed account seems to be 

 available, and it would be desirable to know something more about 

 them, so as to form a judgment as to the weight to be given to 

 the result, before comparing it with the others. 



Lieutenant Elblein gave to Mr. Ellery the following provisional 

 results of his i seconds invariable pendulum observations at 

 Melbourne and Sydney : 



