346 



.YA TURE 



[February 7, 1895 



such explosions, are well known. Mr. Fowler showed ihat 

 it was the ho: water, rather ihan the sleam, in the bjiler 

 which formed the source of destructive energy. In regard 

 to the causes of boiler explosions, there is nothing occult or 

 mysterious. They can, as a rile, bi traceil by pitieni investiga- 

 tion to ih: operation of simple an I well-known facts. Thus 

 when a boiler-shell is normally in a stae of high tension, if 

 once a rupture take-; place by the acti>n of sl.atic stresses on a 

 lotilly weak spot, the store 1-up ener.;y is capable not only of 

 tearing the boiler to pieces, but of producing all the other de- 

 structive effects ob-crvei in connection wiih such disasters. 

 Prou.inent among the principal causes of explosions is the 

 corrosion of the boiler-shell. Some explosions have iheir 

 origin in the stresses arising from expin-iion ani contrac- 

 tion due to the action of the fire. As an illustration of the 

 stresses set up by unequal expansion an 1 contraction in a boiler, 

 a case was mentioned in which an explosion occurred two hours 

 after the fires were drawn. A frequent sou'ce of boiler explo- 

 sions in the past is the practice of cutting large openings in 

 boiler-shells, wiihout providing compensating strengthening- 

 rings. Overheating from shortness of water is a common cause 

 of boiler explosions but the operation of thi> ouse is different 

 from the reason formerly assigned to it. Explosions are not 

 the result of turning c )Id water on to red-hot plates. What 

 takes place is that the overheated plates become gradjally 

 softened, with the result that they bulge downwards and are rent 

 at the ordmary working pressure : explosions of this kind are of 

 a relatively mild character. .Many explosions arise from ex- 

 cessive pressure in conseiuence of the defective action of the 

 3afely-v.ilve. This may o::cur in a variety of ways, but the type 

 of valve loaded with a spring-balance is the most prolific s nirce. 

 Fin.-illy, explosijns sometimes arise from faulty material and 

 construction. As a result of using iron of pojr quality with 

 punched holes, incipient H iws are occasionally set up in the 

 seams, and several cases have occurred in which these inherent 

 defects were so situated as In forbii detection when the boiler 

 was put togcth-r, and were only revealed by the explosion. 

 These defects show the value in connection with new work of a 

 carefal hydraulic test. 



The barometer has been very high over north-west Europe 

 during the past week, and the type nf weather over these 

 islands has been anti-cyclonic, with strong ea-terly winds or 

 gales at several places on our coasts. In the nei^hbourhoril 

 of London the maximum day temperatures have not exceeded 

 35', and at ni);ht rhirp frosts have occurred. In the suburbs a 

 reading of 15° has b.en recorded, and a few miles distant the 

 lemptraiurc fell several degrees lower, with a radiation tem- 

 pcratuie of 6''5, while over the midland districts of England 

 the ihermometer in the shade has fallen 24° below the 

 freezing point. The Wctkly Wtathcr Ref.nt jiulilishcd by the 

 Meteorological Office states that during the week ending the 

 ind ins', the absolute sha-le minima recorded were— 2° at 

 Llandovfry on January 28, 1° at Hraemar on J.inuary 30, and 

 2' at llillington on January 27. Over the whole cmiiitiy the 

 temperature ranged froui 8' lo 13'bcli.w the mean for the week. 

 Snow has fallen at many places in different pans of the king- 

 <lum. 



The beautiful Alpine phenomenon which the Swiss call 

 " Alpengluhen," is nola simple red ^low of the snowy peaks at 

 sunwl, but is sometime* intermittent, the glow returning once 

 or twice after it has apparently died away. Dr. J. Am>ler, in 

 a recent communication to the Swiss Natural Science Society, 

 eiplains Ih's repetition by takin*; into account the various 

 deviations undergone by the sun's rays in passing through the 

 rapidly cooling atmosphere. Since the air is colder in the higher, 

 and warmer in the lower strata, the solar rays undergo a kind 

 NO. 1319, VOL. 51] 



of total reflection which makes them pass upwards again, so 

 that when the sun has reached a certain position they will no 

 longer strike ihi summits. This is llieendofthe first glow. 

 As the lower air cools, the rays become once more rectilinear, 

 and the second glow sets in. When the sun sinks still lower, its 

 rays are thrown down upon the L;laciers by ordinary refraction. 

 This refraction may be intensified by warm air from below 

 reaching the upper regions of the air, which would give rise to 

 the third glow. Kut the latter is only rarely observed. 



It is gratifying to learn that the Italian Government has 

 appointed a commission to study the violent earthquake which 

 occurred in S)uih Italy on November 16. In the meantime, 

 Prof. Tacchini has established one result of great interest and, 

 possibly, of much practical importance (^. Accad. dei Lincei, 

 Rtnd. iii. 1S94, pp. 365-3')7). The earthquake was regis- 

 tered at Rome by three pendulums in the CoUegio Romano. 

 The matimum displacement occurred at jh. 55m. p.m., 

 Greenwich mean time ; but the first movement was registered 

 by the great seismometrograph (length 1611., miss 200 kg.) at 

 5h. 5Zin. 25s., by another (length 6m., mass 100 kg.) at 5h. 

 52m. 30s., and by a third still less delicate (length l\n., mass 

 10 kg.) at 5h. 53m. 20s. Now a clock was stopped at 

 the observatory of Messina at 5h. 52m., there being no 

 slight shock previously, and the miximum disturbance 

 was registered at the same moment at the observatory 

 of Catania. It may be inferred, therefore, that before 

 the great shock took pl.ace, there w.as a microseismic 

 motion insensible to man and to ordinary apparatus. But, if 

 an instrument as delicate as that at Rome had been installed at 

 Messina, the beginning of the motion would have been recorded 

 2\ minutes before the occurrence of the sensible shock. 



\Vk learn from the Journal of Botany, that a " Flora of 

 Berkshire," by Mr. Druce, will shortly be published. 



The constant communication kept up by the central 

 authorities at Kew with the directors of the various colonial 

 botanic gardens, is bearing fruit in the numerous botanical 

 publications which proceed from the Colonies. We have on 

 our table the />«//i//« of MisceUancous Information from the 

 Royal 1! ilanic Garden, Trinidad, for January 1S95 ; the .^f^v- 

 cuUural Joninal of the Leeward Islands for October 1894; 

 and Notes on Antigua tnassts, by Mr. C. .V. IJarher, Superin- 

 tendent of .\griculture for the Leeward Islands ; all containing 

 notes .and information of value for the dwellers in the Tropics. 



Five Biilletim of the University of Wisconsin have come 

 to us. One, the first of a Science Series, is on the speed of the 

 liberation of iodine in mixed solutions of potassium chlorate, 

 potassium iodide, and hydrochloric acid, the author thereof 

 being Mr. II. Schlundt. His experiments show that the speed 

 of the reaction increases lo a marked degicc with temperature. 

 The presence in the mixture of an excess of one or more of the 

 components also increases the speed, and an increase in the 

 degree of concentration acts in the same manner. The pre- 

 sence of hydrobromic acid accelerates the reaction ; and, to a 

 less extent, hydrochloric, nitric, and sulphuric acids. Organic 

 acids, however, and boric acid, do not increase the speed. The 

 four remaining flu/letins referred to belong to the Engineering 

 Series. In one, Mr. L. F. I.oree traces the devtiopmcnl of 

 railroads from 1S25 to the present time, chielly dealing with 

 the construction of the permanent way. Some practical hints 

 in dynamo design are given by Mr. Gilbert Wilkes in the 

 second of the series. The next, by Mr. C. T. I'urdy, refers to 

 the steel construction of buildings ; and the fouith, by Mr. 

 A. V. Abbott, deals with telephones and switchboards. 



Two further communications concerning the new iodine 

 bases are contributed by pupils of Prof. Victor Meyer to the 

 current issue of the B/ri(hl,\ In the fir.st, Mr. John McCrae 



