1842.] Equations of Condition for a Quadrilateral. 211 



visible in the telescope, are still much greater than have ever occurred in 

 practice; for though single sides of more than a degree be nothing very 

 extraordinary, it is but rarely that two such sides can be found forming 

 a triangle with a third side of from 118 to 120 miles. 



19. The difference here treated of is, in similar triangles, proportional to 

 the 4th powers of the homologous sides : Hence, in an equilateral with 



half degree sides, this difference would be -« of 0"-005245, or 0"-00006475 ; 



and on the isosceles with half degree sides containing 120°, the difference 



would be - of 0"-0024176, or 0"-00001511. Triangles such as these are not 



very uncommon, but it is much more common to have triangles with less 

 than half of their area. 



20. It is thus fairly proved that the difference between the excess on a 

 spherical triangle computed rigidly, and that deduced by reckoning its area 

 as equal to that of a plane triangle of the same sides and contained angle, 

 is a quantity so small that, even in extreme cases, the neglect of it will 

 induce no sensible error ; and that in triangles such as usually occur in 

 practice, the difference is so utterly insignificant, that to go much out of 

 the usual way in order to take account of it, would be a very needless 

 refinement. 



Notes regarding the Meteorology and Climate of the Cape of Good Hope. 

 By Robert Trotter, Esq. Bengal Civil Service. 



When last at the Cape it occurred to me, that a few particulars 

 regarding the climate of a place, to which so many resort from this 

 country in search of health, might be found interesting as well as useful : 

 and particularly to medical men, by enabling them to judge how far 

 it is likely to prove beneficial to those patients, for whom they may 

 consider an absence from India necessary. If you deem the accom- 

 panying Meteorological Table, and the following cursory remarks worthy 

 of a place in your Journal, I shall feel obliged by your inserting them. 



The table contains an abstract I prepared from the Meteorological 

 Registers of the Royal Observatory at the Cape, shewing the mean 

 monthly weight and temperature of the atmosphere, and the minimum 

 of each month for three years together, with the monthly fall of rain 

 for the same period ; and in order to compare the results with the 

 climate of India, I have inserted corresponding observations made at 

 Calcutta for an equal period, and likewise the monthly means of a 

 year's observations at several other stations ; viz. Darjeeling, Dacca, and 

 Cawnpore, extracted chiefly from the Journal of the Asiatic Society. 



The Cape observations were made at 3 hrs. 15' p. m., being the period 

 of least atmospherical pressure ; the Thermometers hang on the South- 



