248 



• KNOWLEDGE • 



[April 27, 1883. 



south and south-cast winds which came upon us in Januar}-, 

 did not pass away until the niiddlo of this niontli (Fuli- 

 ruary), and soon after it had gone the wcatlicr continued 

 for some time to rellect its inlluence." We find that tlio 

 south-cast wind is most prcvaU'nt during the spring and 

 summer seasons, and that tlio months during vvhiclx it 

 Mows the greater number of days are March, April, and 

 .1 uno. 



On the Eastern and Southern Coasts, to which it would 

 naturally come first, during the years 1878-79, its fre- 

 quency had a mean of seventeen days, whilst on the WckI 

 Const, during the same period, the mean was twenty-eight 

 days. This anomaly will be explained when we illustrate 

 this sul)ject by wind charts, which will show how many of 

 what are called "prevailing" winds are really nothing more 

 than diverted winds, due to the physical peculiarities of 

 the country around the station where the observations were 

 made. This wind is interesting, as some dependence may 

 be placed upon it when calculating on the chances of fine or 

 bad weather. In fact, it appears that there are two kinds 

 of south-east winds — one the harbinger of wet and stormy 

 weatlier, whilst the other is the forerunner of fine ; and as 

 weather is of great importance to the visitors at the seaside, 

 we will briefly describe the conditions under which this 

 wind may be used as a weather prognostic. When the air 

 is warm and moist, the barometer follows, and the sky 

 clear down to the horizon, or flicked with cirrus clouds, and 

 then covered with grey clouds, rain may be expected ; on 

 the other hand, if the air is dry, as indicated by the wet 

 and dry bulb thermometer, or by the speedy disappearance 

 of steam from a locomotive or other engine, the sky 

 clear, except at the horizon, which is liazy, not cloudy, and 

 the barometer rising, then the south-east will bring fine 

 settled weather. 



This wind comes to us warm, from the heated soil of the 

 north of Africa, and laden with a certain amount of 

 moisture from the Mediterranean Sea. One portion of this 

 wind may travel to us up the Adriatic Sea, and then over 

 the Swiss Alps, which would materially afiect its original 

 character as regards heat and moisture. Another route, 

 however, is taken in a more southerly direction, and then 

 we get it after it has passed through France. The latter 

 is generally the rain-bearing wind, and often veers to the 

 south and south-west, whereas the former portion has a 

 tendency towards the east, thus remaining a dry wind and 

 the source of settled weather. 



Thf !<outh. — This wind, like the last, difiers in its 

 character as it difters in its source and route to our coasts. 

 One portion has travelled over the Pyrenees before tra- 

 versing France ; whilst another belt, after passing over 

 Spain, sweeps across the Bay of Biscay, and has a more 

 marine character than its companion to the east of Ports- 

 mouth. The south wind blows on the east coast about 

 thirty-two days ; on the south, thirty-five ; and on the 

 west, thirty-six days in the year. 



The South Coast throughout its entire length looks 

 towards France, Calais, and Boulogne opposite. Dover- 

 F6camp, which received the fugitive Charles II. after 

 escaping from Brighton in Tallusell's coal-ship, lies in 

 front of Hastings. Opposite tlu; coast, between Beachy 

 Head and Brighton, are Havre and the mouth of the 

 Seine. The Rochers de Calvados, Barfleur, the Channel 

 Islands, and St. Malo lie opposed to the Isle of Wight, 

 Weymouth, and Portland Bill. 



The remaining winds, namely, the south-west, the west, 

 and the north-west, are all eminently sea winds, and will 

 1)0 noticed in our next article, when we purpose concluding 

 this portion of our subject, and illustrating our coastal 

 winds by a scries of charts, constructed with the view of 



explaining how tlie physical features of England and its 

 coasts influence their direction and modify their influence 

 on our climate. 



SECONDARY BATTERIES OR 

 ACCUMULATORS. 



Bv E. C. RniiSGTON". 



rpHE ideas of the general public concerning secondary 

 JL batteries being, to say the least of them, rather hazy, I 

 propose in this article to endeavour to show what a 

 secondary battery really is, and to describe its chemical 

 action. 



A secondary battery or accumulator is a reservoir for 

 storing electrical energy — not, as is popularly supposed, for 

 storing electricity. 



The probable reason why this false idea prevails arises 

 from the fact that, in former times, electricity was believed 

 to be a fluid, and, although it is now known that this 

 cannot be the case, the convention is still often adopted 

 as a convenient method of referring to and studying its 

 actions. Coupling the idea of electricity being a fluid 

 together with the term current of electricity and the analogy, 

 frequently given, between electricity and water, the general 

 public have arrived at the conclusion that a secondary 

 battery or accumulator " stores electricity " much in the 

 same manner that a cistern stores water. This is com- 

 pletely and entirely wrong. An accumulator does not 

 store electricity ; it stores electrical energy by means of 

 chemical decomposition, and it is the reconvertiou of the 

 chemical compounds into their former state that gives us 

 back the energy, absorbed in decomposing them, in the 

 form of an electric current. If we immerse two plates of 

 platinum in a \essel of acidulated water, and then pass a 

 current from one or two Grove cells through this volta- 

 meter, we note that bubbles of gas come ofl' from the sur- 

 faces of the two plates. 



Where does this gas come from ? It cannot be from the 

 platinum plates, because the platinum remains unchanged, 

 however long we continue the experiment ; but in time 

 the water gradually diminishes in bulk ; the gas evolved 

 must, therefore, come from the water — in other words, the 

 water becomes decomposed or split up into the elements of 

 which it is composed. 



Let us now collect the gas given oflT from each plate in 

 two separate tubes. On testing the gases thus collected, 

 we find we obtain hydrogen in the tube over the platinum 

 plate connected to the zinc or minus pole of the charging 

 battery, and oxygen in the other tube, these gases being 

 the elements of which water is composed, its chemical 

 symbol being Hj 0. 



Now let us try the same experiment, but, instead of 

 using a Grove cell, which has an electro-motive force of 

 rO volts, let us employ a Daniellcell, whose electro- motive 

 force is rather over one volt ; we find that no effect is pro- 

 duced. The reason for this is that the electro-motive force 

 of the secondar)- battery formed by the liberated oxygen 

 and hydrogen is greater than that of one Daniell cell 

 (being, in fact, 1 '-lo volts). 



Let us now try our former experiment, but, instead of 

 having short pieces of platinum, let them be prolonged 

 up into the tubes, in which the evolved gases are col- 

 lected. In charging, include a galvanometer in the 

 circuit, and note in which direction the needle is deflected : 

 then disconnect the battery and circuit the voltameter 

 through the galvanometer, when a deflection in the reverse 

 direction will be obtained. This experiment shows that a 

 current can be obtained from this arrangement ; only, of 



