212 



KNOWLEDGE 



[Aug. 



appear to have very differont direotion?. From observa- 

 tions extending over ten years at the following stations on 

 the Norwegian and Swedish coasts, it appears that the 

 n>can air temperature in January at the ponit of dt-parture 

 . f these winds is ^^.T" r>, or 3° 5 less than the isotherm of 

 our west coast (:>"'') during the same month. Thus 

 Ohrtstiansund, C3' 7' Lat X. lias a mean monthly air 

 t.-mperaturo of 31" 3 Fahr. ; Bergen, GO^ 1'4' Lat N. 3:^ 3 ; 

 Skudcnses, 59'' 9' Lat K. Si'"!; and Mandal, S.S" 2' 

 lj>t N., 31" S. lu passing it may be noted that 

 Mandal, although the most southern of these stations, 

 lias a mean January temperature 1° 5 colder than 

 the most northern, Christiansund, which being on the 

 nortii west<?rn coast of Sweden, has the immediate benefit 

 • if the gulf stream. These stations in summer (July) have 

 ;i mean temperature of 55'' 4, or 5° 1 lower than the mean 

 of the four isothernials, 59°, 60^ GT, and 62°, between 

 IJerwick and Cromer ; hence the cooling and refreshing 

 influence of this sea wind in the height of summer on our 

 t-ast coast It must now be observeft that, at a time when 

 the gulf stream influence is ni7, and the sun-heat all 

 powerful on tlie land, the most southern station, Mandal, 

 has a mean air temperature of 58° 9, whilst that of the 

 most northern, Christiansund, is only 54° 4, or a difference 

 of 4° 5. This north-east wind has a large marine element 

 in it 



On the east coast it is the least prevalent of the .sea 

 winds ; it liogins to become more frequent in March, and 

 generally reache.s its maximum in April and IMa\-. Com- 

 pared with the other sea winds we have seen that the per- 

 centage of its prevalence is 12 00 throughout the year. 

 During the mouths of its greatest prevalence, the Norwegian 

 and Swedish stations have a mejxn air temperature of 40° 5 

 in April, and in May 46° 6, while the mean of the isotherms 

 l»ctwcen ISerwick and Cromer are 46° 8 in April and 52° 

 in May, the temperature of the sea for the.sc months being 

 about 42° 7 and 46° 3 rc-pcctively. Thus it is that the days 

 on which this wind blows, a depression in the air tempe- 

 rature is experienced. It is the wind that brings what are 

 calle<l " black frosts " as distinguished from the " white," or 

 hoar frost*, which are eminently local in their character, and 

 the result of unchecked heat radiation under a serene sky. 

 The north-<>ast wind before it reaches our shores has to 

 travel over six or seven hundred miles of sea. 



The western part of Europe must now engage our atten- 

 tion, as over it blows the wind which of all others exercises 

 the most important tflects upon our country. The observer 

 a-s he travels from north to south along our east coast 

 will have opposite to him, within the interlatitudinal 

 Tonf I., Denmark, with its two station.", Tarm and Copen- 

 hagen ; within zonea II. and III., the coast of Germany 

 which unites Deiiiiiari: with the Netherlands ; within 

 mne IV. the Netherlands ; and zone V. Belgium. This 

 <x)ast line is the we.st<m boundary of the great central 

 plain of Europ*-, which is walled in on the east by the 

 ITral mountains, stret'-hing from the north to the south of 

 Europ«-. A wind that has traversf-d such a plain before 

 nracliing our hhoros must have had its marine character 

 '■ntirely altered, and it is a most important question whether, 

 and under what circumstances, it.s short sea passage enables 

 it to recover its title to be called a sea wind. This we shall 

 naierve for our next paper. 



\» <T lo r.Ai;f..rnia, Auatralin i« tho most prwiactive of golrl- 

 ''•■ Tho goM-bcaring U-rritory of Victoria ftlono is 



"liinrf. niil.n; of New Hoalh Wak-H, la.GoO; 

 11,0 i,.)uur.- ioilcii. An in the Ilwky Monn- 

 "• -. cold ii fonnil lx»lh in qoartz-rockand filuccr« ; 



h-it, 1 \r. I. ,. n.iitM of California, those of Aoitrulia arc Ijccominp 

 •rretj jre»r IcM produdiTc. 



ELECTRIC LIGHTING AND ITS RISKS. 



rpiIE rapid development of electric lighting which we 

 L have witnessed during the past year or two has, as 

 might have been anticipated, been accompanied by more or 

 less important misadventures. Koughly speaking, these 

 may be divided into two classes — first, accidents to the 

 body ; second, accidents to property. A few eflbrts have 

 been made to formulate and help guard against the recur- 

 rence of these accidents, the causes for which are, in the 

 great majority of cases, easily disoernilile by practical 

 electricians. There is, however, hardly a subject so 

 importAiit and so frequently ignored by amat(!urs and 

 unpractical men generally as the necessary methods for 

 confining the electric current to the channel through 

 which its course is intended to lie. Its importance is com- 

 parable to the necessity of making strong boilers to confine 

 steam, or of thoroughly washing the glasi^ and other 

 apparatus in the hands of the amateur or professional 

 chemist. 



If the electricity is properly confined or insulated, the 

 chances of danger to the body are reduced to a minimum. 

 These dangers arise only from currents of high intensity 

 such as are used for arc lights ; and the wires transmitting 

 such electricity should not only be carefully insulated, but 

 should be fixed in such a way as to prevent tho compara- 

 tively soft insulating being rubbed away by friction against 

 the corners of houses, tunnels, chimney-stacks, itc. It 

 would be well if some competent authority were employed 

 by Government to fix a legal minimum amount of insula- 

 tion, and to stipulate with tho various companies that 

 fre(|uent, careful, and trustworthy tests should be taken. 

 We e this done, we should hear nothing of such accidents 

 as that which occurred at Hatfield, and which wo cannot 

 stigmatise in milder terms than by calling it barbarous. 

 Should such an authority be appointed, one of its most im- 

 [ o tant duties will be to see that the earth is rarely, if ever, 

 used as a return wire. The dangers to property are of a 

 very did'erent kind. They result from the volume or 

 quantity of the current. When this gets to be more than 

 tlio conductor can sustain, it becomes hot, and may 

 eventually set fire to the building. This we know to have 

 frequently happened, and as it is not always possible to 

 guard against a current getting too large for th(! conductor, 

 an automatic device should be invariably ins('rted by 

 which the circuit is broken and the current no longer 

 allowed to flow. In certain places great stress is laid on 

 a regulation that the conductors should bo at a consideraV)lo 

 distance from each other, but where proper means are 

 taken to ensure thorough insulation, this V>ecomes unneces- 

 sary. Whether anyone is ever appointed for this particular 

 work or not, it is certainly to be hoped that we shall soon 

 have something more definite than tho generalisation to 

 which we were indulged in the report we published a week 

 or two ago. The gross ignorance displayed by very many 

 electric light engineers (!) demands this, and the sooner 

 Kom(^thing is done, the better will it bo for the vendor as 

 well as for the buyer. 



LEARNING TO SWIM. 



Bv Natator. 



{Continued /rom patje IflO.) 



AVING acquired the art of balancing easily in the 

 water, body aslant, back uppermost, you are practi- 

 cally ma.ster of the situation ; for, while the balancing 

 comes easier at every trial, many ways of making progres-H 

 come naturally to you. For instance, if you put the 



H 



i 



