12 Mr. Gamble, Meteorological Note^. [Dec. 4, 



The difference between the hottest and coldest years is greater inland 

 than on the coast. max. min. 



At Aliwal North .. 7-5 8-1 



Port Elizabeth . . 2-9 3-2 



Eoyal Obseivatory 3-2 3-5 



Worcester . . 2-6 3-0 



A curious feature is a hesitation in the annual curve of temperature, 

 both at Maritzburg and Durban, in October and November. This is 

 probably owing to the commencement of the rainy season. 



Inland places get their maximum and minimum temperatures earlier 

 than coast places, the latter having what is called a retarded climate ; 

 this is seen in the diagrams. 



II. Baeometric Observations at the Cape. 



Simultaneous readings of the barometer at 8 a.m. have for some 

 time past been taken at several points along the coast, and telegraphed 

 to the Secretary of the Meteorological Commission, who reduces them 

 to a uniform temperature of mercury, and to what they would have 

 read at sea-level, thus rendering comparisons between them possible, 

 and giving us some idea of which way the barometric gradient runs. 



The question is frequently put, Why do you not include up-country 

 stations ? The reply is that we do not know the la.w of reduction to 

 sea-level. In European weather-charts, pi ices more than a few 

 hundred feet above sea-level are omitted. The formula of Laplace, 

 amended by Bessel and others, applies fairl}^ well to mountains near 

 the coast, but does not apply to elevated table-lands, as has been shewn 

 of the simultaneous observations taken at Clermont and on the Piiy 

 de Dome. The reduction used for low levels cannot be satisfactorily 

 applied to jg;reat heights, and if applied has no physical meaning. 



Until the organization of an annual inspection by the Secretary, the 

 up-country barometric observations were generally untrustworthy. I 

 would except Mr. Hugo's observations at Worcester, and one or two 

 others. To show this, it may be mentioned that when the railway 

 reached King William's Town, the level of the hospital was connected 

 with the rail-level, and found to be 1314 feet above sea. But we had 

 previously supposed from comparison of barometer readings that it 

 was 1647 ! On examination it was found that the hospital barometer 

 had air in it. A similar experience was made at Colesberg bridge. 



In finding heights by barometric readings, it is most important that 

 both summer and winter observations should be taken, as the daily 

 and annual variations of pressure at sea-level are not at all the same 

 as those at five thousand and more feet above the sea. Some years ago 

 I made a long journey in the Colony in an ox- wagon, and I took a 

 travelling mercurial, which I slung and ''guyed" to the roof of the 

 wagon. This journey was in summer time, and I have reason to 

 believe that most of the heights I then calculated are too high. On 

 the occasion of a subsequent journey in wintertime I made the heights 

 of places too low. 



As a test of what may be the errors of barometic measurement of 

 heights, the following examples are interesting. The town of Coles- 

 berg is found by railway levelling to be 4407 feet above the sea. The 

 botanist, Drcge, a very careful observer, is less than one per cent, 

 wrong, he having made it 4430, but this, no doubt, was somewhat 

 fortuitous. Wyley, the geologist, made it five per cent, too low, 4200. 



