on the Climate of the Canary Islands. 99 



of Mons. Borda's voyage, which has been communicated to me 

 by the Bureau of Marine at Paris. Borda had given orders to 

 Mons. Chastenest to sail round the island of Canary, who sailed 

 accordingly with a strong north-east wind from Sardina to the 

 Punta de PAldea. Having got round this point, however, he 

 found himself all of a sudden involved in such a calm, that he 

 required two days to reach the Punta Descojada, only about a 

 league distant. He took four days more to double the Punta 

 d'Arganeguin, the southernmost part of the island. Then, on 

 the following day, he advanced slowly to Cape Tanifet ; but no 

 sooner had he weathered this, than the north-east wind came 

 against him with such violence that he was obliged to take in the 

 greater part of the sails. Now, the line from Punta Aldea to 

 Cape Tanifet lies as exactly at right angles to the direction of 

 north-east, as if artificially laid down. 



Glass investigates how far this interruption extends out to 

 sea, and fixes it at from 20 to 25 leagues for Canary, 15 for 

 Teneriffe, 10 for Gomera, and 30 for Palma. He asserts that 

 he had visited and ascertained all these calm projections, and 

 that they are very dangerous to ships, because the high waves 

 break upon the quiet water of these unruffled spaces, as upon a 

 shelving shore, and occasion a very hazardous and foaming 

 surf. These distances are so very considerable as to justify the 

 belief that these winds do not proceed parallel to the earth, still 

 less that they have their course downwards ; but that they as- 

 cend gradually, or, what is the same, towards low latitudes oc- 

 cupy greater spaces. It were scarcely accountable, on any 

 other supposition, why they should not sooner unite again be- 

 hind the islands. 



Barometrical observations do indeed seem to indicate a parti- 

 cular accumulation of the atmosphere over the Canary Islands ; 

 at least the appearances the barometer presents are, in this re- 

 spect, very deserving of attention, and more careful examination. 



From the 21st July till the 10th August, I daily observed 

 the barometer at Las Palmas in Grand Canary, and found it re- 

 duced to the freezing point. 



g2 



