1837.] the South African Literary and Scientific Institution. 395 



Communications have been received by the Committee from 

 Sir E. Ryan, Chief-Justice of Calcutta, containing a Register of 

 the barometer and thermometer, kept by himself during his passage 

 from Table Bay to Calcutta, in the months of December, January, and 



February 1334-5 ; from Mctlardy, Esq. Surgeon on board the 



Mountstuart Elphinstone, containing 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. Thalia, containing extracts from a Journal of the barometer 

 and htermometer, &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. Innis, Esq. Surgeon 

 on board the Sherburne, containing a similar register kept during the 

 approach to and after the arrival of that ship in Table Bay in Janu- 

 ary 1 835. 



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

 and of Mr. McHardy), it must be observed, that they both, but espe- 

 cially the first, afford strong corroborative, and indeed quite deci- 

 sive, evidence of that important meteorological fact, of a consider- 

 able depression of the barometer in approaching to the equator 

 from extra-tropical latitudes. Sir E. Ryan's barometer, previous to 

 his sailing, was compared, through the medium of a portable ba- 

 rometer in possession of Sir J. Herschel, with the Mural Circle 

 barometer of the Cape Observatory, the difference of which, from 

 the standard of the Royal Society, had been previously ascertained by 

 two distinct comparisons, agreeing perfectly inter se, made by the in- 

 tervention 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 ba- 

 rometer 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 south- 

 wards from the equatorial 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 : — 



Limits of the Zone of Latitude. 



Number of 

 Days' Observa- 

 tions. 



Mean Pressure 

 observed in 

 Inches. 



Mean correspond- 

 ing observed 

 Latitude. 



Equatorial Zone. 









Lat. 5° N. to 5° S. 



7 



29.821 



o° 4r 



_ 5 — to 15 — 



10 



29849 



9 50 



— 15 — to 25 — 



8 



30.0<0 



19 12 



— 25 — to 35 — 



10 



30J25 



31 0 



— 35 — to 40 — 



24 



29.934 



3S 25 



