ON THE DETERMINATION OF GRAVITY AT SEA. r)G?, 



the change in the disposition of the aneroid when mounted on springs, not 

 to the pumping being greater, since equal pumping later on occasioned 

 no such drop in the value of g. Las Palmas shows a high value with a 

 defect on approaching and leaving the island, perhaps because the 

 island is built up of material taken from the neighbourhood, but probably 

 this is accidental. 



(2) The non-success of the reduction of the aneroid for the latter 

 part of the voyage is shown by the impossibly large departure from 

 the theoretical values shown in fig. 12. 



(3) The observations have been corrected by taking those of Cape Town, 

 Fremantle, and Adelaide as reference stations. Plotting the deviations 

 from the theoretical curve against ocean depths, fig. 13 has been obtained. 



The defect of gravity between 0° and Cape Town may be due to the 

 absence of a port of reference to the left of the diagram. It is, however, 

 suggestively in agreement with the Morea readings in deep water, fig. 9. 



(4) The continuity of the observations between Cape Town and Fre- 

 mantle (fig. 13) was broken by various disturbances to the instruments 

 already mentioned, but the average divergence of a reading from the 

 theoretical value is not more than 03 cms. sec.^ ; if these readings stood 

 alone they would support Helmert's formula and Hecker's conclusions, 

 though the probable error is large in this part of the voyage, the differ- 

 ences between successive readings sometimes amounting to suchimprobable 

 values as '6 cms./sec.'^ This may be attributed to the pumping of the 

 mercury barometer, which was so large that a very large proportion of the 

 readings would have been omitted if the same standard had been demanded 

 as was required for the Morea observations. The pumping of the aneroid 

 was, however, within the limits allowed. Between Fremantle and Ade- 

 laide the theoretical formula is followed approximately, high values being 

 observed as the ship rounded Cape Leeuwin, as in the Mo/m observations. 



11. Temperature Regulation on Board Ship. 



The Interim Report of the Committee (1915) paid a tribute to the 

 generosity of Messrs. Alfred Holt & Sons, of the Blue Funnel Line of 

 steamships, for erecting a special chamber for these experiments in the 

 refrigerator of ss. Ascanius. 



The chamber was conveniently situated on the level of the dining 

 saloon, and was a little above sea-level. Access to it was through the 

 ' handling- room, ' which was at a temperature of about 40'' F. The chamber 

 liad its own system of brine pipes, which could be connected up to an 

 auxiliary engine, and it was possible to adjust the number of pipes in 

 operation within the chamber. 



An electric fan placed on the floor kept the air stirred continuously 

 within. The temperature was read from without by a thermometer 

 which could be withdrawn through a hole in the wall. This was read 

 at intervals seldom greater than one hour throughout the whole of the 

 twenty-four hours by one of the refrigerating engineers, and brine 

 pumped through accordingly. 



Fig. 15 is shown as an example of the success achieved in regulating 

 and in compensating for the entrance of the observer. I am indebted 

 to Mr. Latham for this diagram, which was drawn from his observations. 

 It will be seen that it is possible to maintain an experimental chamber 



