108 REPORT — 1867. 



On the Meteorology of Port Louis in the Island of Mauritius. 

 By Charles Meldrum, M.A. 



[A communication ordered to be printed in extenso.'\ 



MATJEiTiirs Kes nearly between the parallels of 20° and 21° S. latitude and 

 the meridians of 57° and 58° E. longitude. With the exception of the small 

 islands of Reunion, Eodrigues, and the Cargados, which are from 100 to 300 

 miles distant, the nearest land is Madagascar, about 500 miles due west. 

 The nearest point of Africa is about 1100 miles W. b. N., and of India about 

 2000 mUes N.E. b. N. Towards the E.N.E., E., and E.S.E., are the Indian 

 archipelago and Australia, at distances of 2600 to 3400 miles ; while to the 

 southward an almost unbroken ocean stretches away to the polar seas. 



Thus surrounded by a great expanse of ocean, especially to windward, 

 Mauritius may be regarded as a locality in which the meteorological elements 

 may be determined in a form comparatively free from the complications 

 caused by neighbouring masses of land. 



The island itself, -which is of volcanic origin, has an area of 700 square 

 miles, and is of an oval form. Its greatest length is 39 miles, and its 

 greatest breadth 34 miles. Nearly one-third of it is under the cultivation 

 of the sugar-cane, the other two-thirds consisting chiefly of pastiu-age, 

 forest, and mountaia. In the interior, and more or less surrounded by three 

 chains of mountains, varying from 1000 to nearly 3000 feet in height, and 

 sending off spurs towards the coast, is a tableland, -which attains an eleva- 

 tion of 800 to 1400 feet, and a considerable portion of which has of late 

 years been planted with the sugar-cane, the primeval forests having, to a 

 great extent, been cut down for the purpose. Between tlicse mountain- 

 chains and the shore, particularly in the northern parts of the island, are 

 plains generally covered -with sugar-cane, and gently sloping to the sea, 

 above which they are but little elevated. For beauty and variety of scenery, 

 for bold mountains, generally clothed halfway up their steep sides with ever- 

 green trees and shrubs, and rearing their naked heads against skies of the 

 softest blue, for rugged precipices, fantastic knolls, peaks, and ridges, for 

 tangled forests, deep ravines and caverns, picturesque waterfalls, shady groves, 

 and rich fertUe plains and valleys, this little island is perhaps unsurpassed. 



The Observatory is situated on the west side of the harbour of Port Louis, 

 on the north-west coast of the island, in 20° 9' 5G" S., and 57° 29' 30" E. 

 It stands upon a coral-rock. Erom "NY.S.W. to E.N.E., through the east, it 

 is suiTOunded by a chain of mountains rising to the height of 700 to 2707 

 feet. As these mountains bear in the direction from -which the prevailing 

 -wind blows, and are only from a quarter of a mile to a mile and a half dis- 

 tant, the position of the Observatory is not very favourable. 



The observations which form the basis of this communication embrace a 

 period of seven years, namely 1860 to 1866 inclusive. 



There are two classes of observations, — 1st, observations taken daily at 

 3| A.M., 9| A.M., 3| P.M., and 9| p.m. ; and, 2nd, observations taken hourly 

 on the 21st of each month. 



The former are referred to as the six-hourly observations, and the latter as 

 the term-day observations. 



As the principal use of the term-day observations is for determining the 

 epochs of the turning-points and the range of the meteorological elements 

 in their diurnal march, they are not, like the six -hourly observations, dis- 



