92 REPORT— 1868. 
case the sun falls and the wind blows upon the margin of a land that rises rapidly 
to 6000 feet of elevation, and then stretches away for thousands of miles, getting 
ever more and more scorched by the intertropical sunshine. <A very instructive 
opportunity is thus afforded for instituting upon a grand scale a careful comparison 
of the insular and continental conditions and influences. A long and sustained 
series of observations is required to do full justice to this comparison. A few note- 
worthy deductions may in the meantime be gathered as “ first fruits” of the in- 
vestigation. 
The actual rainfall is not very different for Port Louis, the capital of the Mauri- 
tius, and for Maritzburg, the capital of Natal. During a series of eight years it 
amounted to 241-79 inches, or 20 feet 1} inch, at the observatory at Maritzburg, 
and to 32433 inches, or 27 feet, at the observatory at Port Louis. The mean 
annual fall for this period was 30-22 inches for Maritzburg, and 40°54 inches at Port 
Louis. Both stations are placed, so to speak, away from the first impingement of 
the moist sea-breeze. But the site of observation at Port Louis is less than 50 
feet above the sea, and that at Maritzburg is 2095 feet above the sea. 
In the Mauritius, in the very limited area restricted in the longest extent to 
thirty-five miles, there are spots that actually receive four times as much rain as 
others. Thus in the year 1862, while the fall was 28-3 inches in the north-west, 
52-2 inches on the north, and 69 inches in the interior of the island; at the south- 
east extremity, at an elevation of 960 feet, it was 1225 inches. 
In the colony of Natal the difference between the coast and the capital, more 
than forty miles inland and more than 2000 feet high, is only as 2to-l. In one 
case of careful comparison, when the fall at the Port of Durban was 22°59 inches, 
the fall at Maritzburg was 11-75 inches. 
In the Mauritius there is a considerable difference in the amount of rainfall in 
different years. Ina series of eight years the least yearly rainfall at Port Louis 
was 20°5 inches, and the greatest 68-7 inches. In a similar range of eight years 
the least annual fall at Maritzburg was 22°4 inches, and the greatest annual fall 
37:3 inches. 
In the Mauritius the rainfall distinctly increases with elevation up to nearly 
1000 feet. 
In Natal the greatest fall certainly takes place on the windward side of the land, 
that is, on or near the coast ; and it then diminishes rapidly with elevation. 
There are no observations yet available to give the fall for the range of country 
intermediate between Durban and Maritzburg; but there certainly is no spot 
where the rainfall materially exceeds that of the district near to the sea itself. 
The large tract of heated land along which the sea-breeze has to rise, seems at once 
to give the atmosphere more vapour-sustaining power, until the ascent becomes 
sufficiently energetic and turbulent to give rise to the periodically recurring 
thunder-storm. 
The seasonal distribution of the rainfall is remarkably regular on the border of 
the African continent, that is, at Natal. There is a distinct division of the year 
into a wet season and a dry one; and the wet season most beneficently corresponds 
with the summer half of the year. Four-fifths of the rain in Natal falls between 
the beginning of October and the end of March, and one-fifth between the begin- 
ning of April and the end of September. The midwinter months of June and July 
are almost dry. In the two months before and two months after these, the rain- 
fall is 1} inch for each month. In the six summer months it averages 4} inch for 
each month. In the Mauritius 58 per cent. of the rain falls between December 
and March, and 42 per cent. during the other eight months. In Natal December 
is the wettest month of the year ; in the Mauritius February is the wettest month. 
The rainfall in the Mauritius is more concentered in the middle of the summer 
than it is in Natal, and is occasionally raised to a great extent in February by the 
occurrence of hurricanes. 
In the Mauritius June and July are dry months, as in Natal; but there is there 
a sort of second dry season after August. October and November are dry in the 
Mauritius, but distinctly and emphatically wet in Natal. 
In both situations the general tendency is to increased rainfall with increase ot 
temperature, and therefore of sea evaporation, which mounts to the highest point 
