the South African Literary and Scientific Institution. 241 



of the Barometer and Thermometer, kept by himself during his 

 passage from Table Bay to Calcutta, in the months of Decem- 

 ber, January, and February 1834-5 ; from McHardy, 



Esq. Surgeon on board the Mountstuart Elphinstone, contain- 

 ing a similar register made in the voyage of that ship from 

 Table Bay to London, during parts of the months of September 

 and October 1834; from Captain Wauchope of H.M.S. Thnlia, 

 containing extracts from a Journal of the Barometer and Ther- 

 mometer, &c. observed on board of H.M.S. Eurydice, off Sal- 

 danha Bay, during a heavy gale in 1819, as also in Table Bay 

 during a violent north-wester in 1817; and, lastly, from H. W. 

 Innes, Esq. Surgeon on board the Sherburne, containing a si- 

 milar register kept during the approach to and after the arrival 

 of that ship in Table Bay in January 1835. 



Of the two former of these communications (those of Sir E. 

 Ryan and of Mr McHardy), it must be observed, that they 

 both, but especially the first, dfford strong corroborative, and 

 indeed quite decisive, evidence of that important meteorological 

 fact, of a considerable depression of the barometer in approach- 

 ing to the equator from extra-tropical latitudes. Sir E. Ryan's 

 barometer, previous to his sailing, was compared, through the 

 medium of a portable barometer in possession of Sir J. Her- 

 schel, with the Mural Circle Barometer of the Cape Observa- 

 tory, the difference of which, from the standard of the Royal 

 Society, had been previously ascertained by two distinct com- 

 parisons, agreeing perfectly inter se, made by the intervention 

 of the above-mentioned portable barometer, which had been 

 brought to the Cape by Mr Henderson, and again transported 

 by him to London. By these comparisons, it was found that 

 Sir E. Ryan''s barometer required a correction of — 0.116 in. 

 to reduce it to the Royal Society's standard. This correction 

 being applied, and the reading so corrected being reduced to the 

 freezing temperature, and classed into groups in zones of 10° in 

 breadth, proceeding northwards and southwards from the equa- 

 torial zone (between the latitudes 5° N. and 5° S.) according to 

 the observed latitudes of the ship at noon of each day, give as 

 follows : — 



