170 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY. 



ment Hyetograpliy — it is stated, on the authority of Captain 

 King, E.N., that upwards of twelve feet (one hundred and fifty- 

 three inches) of rain fell in forty-one days on that part of the 

 coast of Patagonia which lies within the sweep of the wdnds just 

 described. So much rain falls there, navigators say, that they 

 sometimes find the water on the top of the sea fresh and sweet. 

 After impinging upon the cold hill-tops of the Patagonian coast, 

 and passing the snow-clad summits of the Andes, this same 

 wind tumbles down upon the eastern slopes of the ranges as a 

 dry wind ; as such, it traverses the almost rainless and barren 

 regions of cis- Andean Patagonia and South Buenos Ayres, Plate 

 VIII. These conditions, the direction of the prevailing winds, 

 and the amount of precipitation, may be regarded as evidence 

 aff'orded by nature, if not in favour of, ceiiainly not against, the 

 conjecture that such may have been the voyage of this vapour 

 through the air. At any rate, here is proof of the immense 

 quantity of vapour which these winds of the extra-tropical 

 regions carry along with thein towards the poles; and I can 

 imagine no other place than that suggested, whence these winds 

 could get so much vapoui'. 



356. The question. How can two currents of air cross ? answered. — 

 Notwithstanding the amount of circumstantial evidence that has 

 already been brought to show that the air which the north-east 

 and the south-east trade-wdnds discharge into the belts of equa- 

 torial calms, does, in ascending, cross — that from the southern 

 passing over into the northern, and that fi-om the northern pass- 

 ing over into the southern hemisphere (see Q E S, and 

 D E F G, § 215) — yet some have implied doubt by asking the 

 question, " How are two such currents of air to pass each 

 other ?" And, for the want of light upon this point, the cor- 

 rectness of my reasoning, facts, inferences, and deductions has 

 been questioned. In the first place, it may be said in reply, the 

 belt of equatorial calms is often several hundred miles across, 

 seldom less than sixty ; whereas the depth of the volume of air 

 that the trade-winds pour into it is only about three miles, for 

 that is supposed to be about the height to which the trade-winds 

 extend. Thus w^e have the air passing into these calms by an 

 opening on the north side for the north-east trades, and another 

 on the south for the south-east trades, having a cross section of 

 three miles vertically to each opening. It then escapes by an 

 opening upv,^ard, the cross section of which is sixty or one hun- 



