May 28, 1874J 



NATURE 



65 



cable over the same drum which before was used to pay 

 it out ; thus it is coiled back into the same tank whence 

 it started. By this means the necessity of passing the 

 cable astern before proceeding to haul it in is avoided. It 

 was during this operation that an accident befell the 

 Atlantic cable in 1865, causing its loss for the time. 



The ne.xt apparatus is a dynamometer, consisting of 

 three pulleys, one fixed, and the centre one, which rests 

 on the cable, movable in a vertical plane ; by this the 

 strain is registered and adjusted. After passing this the 

 cable runs into the sea over a pulley carried on girders 

 and constructed so as to swing (reely on an axis parallel 

 to the length of the ship, so that, should the vessel make 

 lee-way, the pulley will follow the direction of the cable, 

 and thus friction and sharp bends are avoided. The 

 bows are also fitted witli a similar pulley, compound 

 machine, and dynamometer. We see that by these 

 devices the cable is kept perfectly under control, and 

 should a fault be discovered a simple process of reversal 

 of ship and machinery brings home the faulty portion. 



Another great point is to keep the vessel trimmed and 

 steady. For the former requirement nine separate water- 

 tight compartments, including the cone in each tank, whicli 

 also is hollow, are provided, so that water may be ad- 

 mitted as the tanks arc emptied of cable, and thus the 

 ship is kept trimmed. To ensure steadiness and avoid 

 the rolling to whicli telegraph ships are subject, two bilge 

 keels are set on at an angle of 45*^ ; this was done at the 

 suggestion of Mr. Wni. Froude, whom, said the lecturer, 

 " 1 have to thank for valuable advice and assistance on 

 several new points connected with the Faraday." 



A steam-launch is carried on deck, whence she can be 

 lowered into the water with steam up, ready to land shore 

 ends and perform other useful details. 



Another class of work for which the vessel is titted is 

 '•grappling" for lost or faulty cable. In shallow seas 

 this is a very simple operation, but in deep water it is 

 rather a delicate matter, and requires the co-operation of 

 two or even three vessels, so as to lift the cable without 

 forming an acute angle, and thus to lessen the chance of 

 fracture or strain. A special rope made of steel wire and 

 hemp, and of great strength, is provided for this kind of 

 work. Some specimens shown could bear strains up to 

 16 tons. 



In conclusion, the lecturer paid a high comphment to 

 the late Prof. Faraday, noticing the great services he had 

 rendered to electrical science, his singleness of purpose, 

 and the invariable kindness wi'.li which lie had encouraged 

 younger labourers in the same field. The friendly en- 

 couragement which he himself had experienced from him 

 would ever remain a most pleasing remembrance. He 

 had seized with delight on the present opportunity to pay 

 a tribute to tlie honoured name of Faraday, and was 

 happy to be able to do this with the full consent of the 

 revered lady who had stood by the philosopher's side for 

 forty years, while labouring under this very roof for the 

 advancement of knowledge. The name of the vessel 

 and her mission in the service of Science would combine, 

 he thought, to create an interest in her favour in the 

 minds of the members of the Royal Institution, and he 

 hoped that on the morrow she would put to sea accom- 

 panied by the earnest wish, " God speed the Faraday." 



ATMOSPHERIC CURRENTS AS OBSERVED 

 IN THE WEST INDIES, AND PARTICU- 

 LARLY IN ST. THOMAS 



DURING an average period of nine months in the year 

 tl»e regularity of the air-currents over the Virgin 

 group resembles clockwork. The surface, or lowest cur- 

 rent, is formed by the trade-wind, which blows briskly 

 from the north-north-east, with a slight variation north- 



ward during the night and early morning, and a corre- 

 sponding deflection south^vard from noon till near sunset. 

 Varying in strength from a light breeze to a brisk gale, it 

 is hardly ever absent ; its greatest strength is usually at 

 or near 3-4 a.m., and about the same hours p.m. It gene- 

 rally bears with it light masses of cumulus, from which 

 there fall occasionally showers, heavy, but very short in 

 duration. This air-current, known as the trade-wind of 

 these regions, does not appear to exceed 2,000 feet in 

 vertical height. 



Next above this current comes the south-west wind, 

 rarely absent ; it brings with it- light cirrus clouds, but 

 seldom cumulus or other indications of rain ; its e>;cess 

 of moisture having been probably discharged while cross- 

 ing the mountains of the South American continent. 

 ^'ery rarely, indeed, does this wind descend low enough 

 to have effect on or even near the surface ; when it does 

 so, which generally occurs during the summer and autumn 

 months, it is deflected to the south, and then becomes 

 loaded with moisture, and accompanied by heavy nimbus 

 clouds and electric phenomena. 



Highest of all the west wind reigns, manifested by very 

 light cirrus clouds, rapidly formed and as rapidly disap- 

 pearing ; it has at times a slight deflection to the north. 



These three winds blow with scarcely any intenuption 

 from November to June inclusive ; almost the only varia- 

 tion being then afforded by the north or north-north-east 

 wind which sometimes prevails, but near the surface only, 

 for a few days together during three winter months. When 

 — a rare but much-desired event — a southerly current oc- 

 curs about this lime, it brings heavy clouds and abundant 

 rain. While the wind is from the north and north-east, 

 great dryness is indicated by the hygrometer. 



But in the months of August, September, and October, 

 and often in the latter half of July, the polar or north- 

 east current loses its strength, and is often neutralised or 

 even conquered by the southerly winds. These during 

 the summer are usually light, and accompanied by a 

 clear and serene sky, only clouded when the north-east, 

 regaining for a time its supremacy, drives the south back, 

 and precipitates heavy showers, amid thunder and light- 

 ning, sometimes lasting for three or even four hours ; 

 after which the wind veers round again to the south-east 

 and south. The same phenomena, when intensified, con- 

 centrate themselves into a hurricane or cyclone — a rare 

 occurrence in this island, not more than four of any great 

 severity having taken place at St. Thomas in the course 

 of the present century. Two indeed, but only of medium 

 violence, occurred within these regions last year ; neither 

 of them however visited .St. Thomas, the one keeping out 

 to sea eastward, and not touching the coast till it reached 

 lat. 44° in its northerly course ; the other, which seems to 

 have originated within the Caribbean Sea, did consider- 

 able damage on the coasts of St. Domingo and Cuba, 

 passing ultimately north-east by the Florida Channel. Of 

 both I have given details elsewhere (vol. ix. p. 468). 

 Heavy gales, occasionally amounting to storms, sometimes 

 blow here, particularly during the winter months, from 

 between north and north-east, but from no other quarter 

 of the compass. They are accompanied by cold, the ther- 

 mometer sinking to 74'" F., or even lower, with a dull, 

 cloudy sky, and little rain. 



Another phenomenon, peculiar to the winter and spring 

 months, are white squalls ; they take place on calm days, 

 generally at noon, and most often at no great distance 

 from shore ; their area is very limited, and their duration 

 does not exceed a few minutes ; in some respects they 

 resemble a miniature hurricane, and appear to be due to 

 similar causes ; but neither have I witnessed in them nor 

 heard recorded any instance of circular motion. They 

 are much dreaded by the sinall craft of these seas ; a 

 slight lall of the barometer is their only premonitory 

 indication. 



St. Thomas W. G. Palgravk 



