EL HOyCADOtt. 203 



the climate of the neighbouring land; but it is less easy to 

 conceive that those slight changes of temperature (for 

 instance, a centesimal degree on the bank of La Vibora), 

 can impart a peculiar character to the atmosphere of the 

 shoals. May not these submarine islands act upon the for- 

 mation and accumulation of the vesicular vapours in some 

 other way than by cooling the waters of the surface ? 



Quitting the bank of La Vibora, we passed between the 

 Baxo Nuevo, and the light-house of Camboy; and on the 

 2 2nd March, we passed more than thirty leagues to west- 

 ward of El Koncador (The Snorer), a name which this shoal 

 has received from the pilots, who assert, on the authority of 

 ancient traditions, that a sound like snoring is heard from 

 afar. If such a sound be really heard, it arises, no doubt, 

 from a periodical issuing of air compressed by the waters in 

 a rocky cavern. 1 have observed the same phenomenon on 

 several coasts, for instance, on the promontories of Teneriffe, 

 in the limestones of the Havannah,* and in the granite of 

 Lower Peru, between Truxillo and Lima. A project was 

 formed at the Canary Islands, for placing a machine at the 

 issue of the compressed air, and allowing the sea to act 

 as an impelling force. While the autumnal equinox * is 

 everywhere dreaded in the sea of the West Indies (except 

 on the coast of Cumana and Caracas), the spring equinox 

 produces no effect on the tranquillity of those tropical 

 regions: a phenomenon almost the inverse of that observ- 

 able in high latitudes. Since we had quitted La Vibora, 

 the weather had been remarkably fine; the colour of the sea 

 was indigo-blue, and sometimes violet, owing to the quan- 

 tity of medusae and eggs of fish (purga de mar) which 

 covered it. Its surface was gently agitated. The thermometer 

 kept up, in the shade, from 26 to 27"; not a cloud arose on 

 the horizon, although the wind was constantly north, or 

 N.N.W. I know not whether to attribute to this wind, 

 which cools the higher layers of the atmosphere, and there 

 produces icy crystals, the halos which were formed round 

 the moon two nights successively. The halos were of small 

 dimensions, 45 diameter. I never had an opportunity of 

 seeing and measuring anyf of which the diameter had at- 



* Called by the Spanish sailors " El Cordonazo d" San Francisco." 

 f In Captain Parry's first voyage, hulos were measured round the sun 



