74 



KNO^VLEDGE ♦ 



[June 30, 1882. 



WEATHER CHARTS FOR WEEK ENDING SUNDAY, JUNE 25. 

 Sunday, 18th. 



Monday, 19th. 



Tuesday, 20Tn. 



Wednesday, 21st. 







TiiuKSDAY, 22nd. 



FlilDAY, 23ed. 



Saturday, 24Tn. 



Sunday, 25Tn. 



In the above charts the dotted lines are "isobars," or lines of equal barometrical pressure, the values which they indicaio being- 

 giren in figures at the end, thus — 30-J. The shade temperature is given in figures for several places on tho coast, and the weather i» 



recorded in words. The arrows fly with the wind, the force of which is shown by tho number of barbs and feathers, thus: — ^- 



light ; ^ , fresh or strong ; y > , a gale ; >j > , a violent gale ; signifies calm. Tho state of the sea is noted in capita) 



letters. The • denotes the various stations. The hour for which each chart is drawn is C p.m. 



Tt is ftated tljat within tho last few months a representative of 

 the Chicago, Slilwankce, and St. Paul liailway has purchased in 

 England about 20,000;. worth of machinery for the new carriage 

 shops of the company. 



Some old bricks having been observed to affect the compass- 

 needle by Ucrr Kepner, at Salzbnrg, in the Tyrol, ho then had two 

 bricks made from each of eight varieties of clay in the neighbour- 

 hood, one brick in each case being baked. Tho unbaked bricks did 

 not affect the needle, but seven of the eight baked bricks proved 

 polarly magnetic. Some further experiments have been made by 

 Hcrren Kell nnd Trientl. Particles of X)Owder of tho magnetic 

 bricks adhered to a steel magnet. Breunerite. mica-slate, argilla- 

 ceous iron-garnet, chlorite, and hornblende were, before heating, 

 anmagnetir, but intense heating produced a magnetic polarity, 

 the axis of which seemed to bo perpendicular to the plane of 

 stratification. 



In a recent lectnro on some of tho dangerous properties of dusts. 

 Professor Abel, F.R.S., said that many experiments were tried 

 with sensitive coal-dust from 8eaham and other collieries for tho 

 purpose of asrertalning whether results could be obtained support- 

 ing the view that coul-dnst, in the complete absence of fire-damp, 

 ia susceptible of originating explosions and of carrj-ing them on 

 indefinitely, as suggested by some observers; but, although decided 

 eridencc was obtained that coal-dnst, when thickly suspended in 



the air, will be inflamed in the immediate vicinity of a largo body 

 of flame projected into it, and will sometimes carry on tho flamo 

 to some small extent, no experimental results furnished by these 

 experiments warranted the conclusion that a coal-mine explosion 

 could bo originated and curried on to any considerable distance ii> 

 the complete absence of fire-damp. Some experiments made in a 

 large military gallery at Chatham showed that tho flame of ai 

 blown-out shot of IJ lb. or 2 lb. of powder miglit extend to a 

 maximum distance of 20 ft., while in a very narrow gallery, similar 

 to a drift-way in a mine, tho flame from corresponding charges' 

 extended to a maximum distance of 3.5 ft. These distances aro 

 considerably inferior to those which flame from blown-out shots ha» 

 been known to extend, with destructive results, in coal-mines, and 

 there appears no doubt that, in tho latter cases, of which tho- 

 lecturer gave examples, tho flame was enlarged and prolonged by 

 tho dust raised by tho concussion of tho explosion. But in th» 

 presence of only very small quantities of fire-damp, dust may 

 establish and i)ropagrfte violent explosions; and that, in tho case- 

 of a fire-damp explosion, tho dust not only, in most instances, 

 greatly aggravates tho burning action and increases tho quantity- 

 of after-damp, but that it may also, by being raised and swept 

 along by the Ijinst of an explosion, carry tho fire into workings 

 where no fire-damp exists, and thus add considerably to the mag- 

 nitude of the disaster. 



