520 



NATURE 



\_April 2^, 1876 



The following diagram, which is not, however, taken from 

 the report, will explain the method : — 



K, battery of 80 cells, well instihited ; R resistance of 20,003 units ; r', 

 variable resis'ance ; c, condenser of 80 microfarads' capacity ; g, 

 shunted galvanometer ; E, earth. 



The condenser is electrified by bringing F and A into 

 contact, and the cable by making contact between H and 

 B, for sufficiently long time to fully charge the cable. 

 These contacts are then broken, and instantly after con- 

 tact made between F and H. This contact is maintained 

 for five to ten seconds, when the additional contact with g 

 is made. The variable resistance is adjusted till this last 

 contact produces no movement on the measuring instru- 

 ment. 



It was found that when the cable and condenser were 

 charged to opposite potentials in the proportion of 1,615 

 to 20,000 no throw occurred, whence the deduction that 

 the capacity of the cable was 



— X 80 microfarads, or 

 1615 ' 



991 microfarads, and the length of the cable being 2,420 

 knots, this was equal to 0*409 of a microfarad per knot. 



In concluding the report upon the electrical conditions 

 of the Direct United States Cable, Sir William Thomson 

 remarks : " I am glad to be able to say that my tests 

 proved the cable to be in perfect condition as to insula- 

 tion, and showed its electrostatic capacity and copper 

 resistance to be so small as to give it a power of trans- 

 mitting messages, which, for a transatlantic cable of so 

 great a length, is a very remarkable as well as valuable 

 achievement." This article would be exceeding its pur- 

 pose if it were to include inquiry into the present position 

 of Atlantic Telegraphy ; but it is a mark of great progress 

 in electrical engineering and cable manufacture that a 

 cable of such length as 2,420 miles can be delivered up 

 to the company working it in a perfect electrical condi- 

 tion. This has not been the case in earlier transatlantic 

 attempts ; and some idea may be formed by the general 

 reader of the care required to bring about this end, when 

 it is known that a small hole, smaller in size than the 

 finest pin-hole, in any portion of the two thousand miles 

 length of gutta-percha covering would render the electri- 

 cal conditions of the cable imperfect. 



THE CLIMATIC CHARACTERISTICS OF 

 WINDS AS DEPENDENT ON THEIR 

 ORIGIN^ 

 C\^ the climatic characteristics of winds the most 

 ^-^ important are, primarily, their temperature, and, 

 secondarily, their moisture. The general occurrence of 



' Ueber die Abhangigkeit des Klimatischen Charakter^ der Winde von 

 ihrem Ursprunge. Von Dr. W. Kiippen. (St. Petersburg, 1874.) 



certain characteristics, especially when more strongly 

 marked, with particular directions of the wind, expe- 

 rience soon forces on our attention, and much labour has 

 been bestowed, particularly by Dove, in grouping the 

 winds simply according to their directions, and calcu- 

 lating the mean atmospheric pressure, temperature, 

 humidity, cloud, and rainfall, for each of the directions. 

 Interesting and to some extent valuable results have been 

 obtained from these inquiries ; results, it must, however, 

 be added, far from being commensurate with the enor- 

 mous labour expended in arriving at them. But in 

 extending this line of research into such regions as 

 Western Norway, Faio, Iceland, Newfoundland, and the 

 Azores, its unsatisfactoriness soon becomes evident ; and 

 the further consideration that the cUmatic qualities of a 

 particular wind repeatedly differ widely from its general 1 

 character, makes it evident that a climatic inquiry which 

 groups the winds merely according to their direction does 

 not proceed from a scientific basis. 



A striking case, showing a great deviation from the gene- 

 ral qualities of a wind, occurred during the great Edinburgh 

 hurricane of the 24th of January, 1868, on which occasion 

 the wind remained persistently in the south for several 

 hours, and possessed a coldness and a dryness which 

 were truly polar. The qualities of this south wind are 

 readily explained by the limited area of high pressure, 

 which lay immediately to the south-eastward of Scotland 

 at the time, out of which this wind blew. As the baro- 

 meter continued to fall, the wind ultimately veered to 

 S.W. and W., and the temperature presented the unusual 

 phenomenon of rapidly rising with a change of the wind 

 into westward. The point to be noted here is, that as 

 long as the wind was connected immediately with the cir- 

 cumscribed area of high pressure it was cold and dry, but 

 when it was involved in the area of low pressure it be- 

 came mild and moist. This relation between the climatic 

 qualities of a wind and the state of the pressure is a 

 vital point in atmospheric physics, and to Dr. Koppen 

 belongs the merit of applying the principle in inau- 

 gurating a new method of inquiring into the climatic 

 characteristics of the different winds by referring each 

 wind-observation to the system of atmospheric pressure 

 with which it is at the moment immediately connected. 



If we examine weather-charts representing a large por- 

 tion of the earth's surface, such as those published in the 

 yoiirnal of the Scottish Meteorological Society, vol. ii. 

 p. 198, two distinct systems of pressure are seen, which 

 change their position and form from day to day, one indi- 

 cated by isobars inclosing spaces of low pressure, into 

 which the winds all round blow vorticosely in the northern 

 hemisphere in a direction contrary to that of the hands of 

 a watch, and the other by isobars inclosing areas of high 

 pressure, out of which the winds blow on all sides, but in 

 opposite directions to those assumed in blowing inwards 

 upon a space of low pressure. The former are usually 

 called cyclones, and the latter anticyclones. Not only do 

 the direction of the winds within the areas of cyclones 

 and anticyclones respectively differ from each other, 

 but the temperature and humidity of the winds con- 

 nected with each have certain well-marked characteris- 

 tics. A south-east wind at St. Petersburg, for instance, 

 blowing in immediate connection with a cyclone, comes 

 from the south and south-west, that is, from the south- 

 west of Russia or from Germany ; whereas a south-east 

 wind in immediate connection with an anticyclone comes 

 from the east, that is, either from the east of Russia or 

 from the White Sea, and consequently these two south- 

 east winds are markedly different in their chmatic qualities 

 from each other. 



Dr. Koppen has compared the temperature, humidity, 

 and other weather conditions at St. Petersburg each day 

 for 1872 and 1873 with daily weather-charts constructed 

 for the whole of Europe, and separated each of the eight 

 winds (N., N.E., E., &c.) and calms into the following 



