M.\Kcn 1, 1901.] 



KNOWLEDGE 



11) 



#€iM€£.llTERATl)RLAARi'/ 



Founded by RICHARD A. PROCTOR. 



Vol. sxiv.] LONDON : MABCH 1, 1901. [No. 185. 



CONTENTS. 



Bv tho Ef>T. John "SI. 

 Bv Geo. H. 



Exploring the Thunder Cloud. 



Bacov, f.r.a.s. {Illustrated) 



The Insects of the Sea. — II. Spring tails. 



C.^BPEN'TKU, IS.Si .Cl.OND.) (Illiislraleil) 



Rainfall in South Africa. B_v Arthcb II. Bbi.i. 



The Size of Ocean Waves. — II. By Vacoua:? Cobnish, 



M.SC.(VICT.), F.C.S., F.B.G.S 



Constellation Studies. — III. The Region ot Virgo. By 



E. Walter JiArxDKR, f.r.A.s. {Illustrated) 



Total Solar Eclipses of the Twentieth Century. 



By A. C. T). CROJfMEr.ix. (Illustrated) 



Sunrise on the Sea of Plenty. l!r V.. Wat.tkr 



Macndbr, f.r.A.s. {Illustrated) 



Sunrise on the Sea of Plenty. {Plate.) 

 Letters : 



fng Path of the ^^rv. By AV^r. Santif.max ... 



SrssET Phenomenon. By R. L. Mf Donald 



Notes 



Notices of Books 



Books Kf.of.ivkd 

 British Ornithological Notes. Conclurteil liy Uabhy V. 



WlIHBRET, F.Z.S., iT.B.O.C 



Finger-Prints as Evidences of Personal Identity. 



By R. Ltdkkker. [Illustrate:)) 



Microscopy. ComUutcd by if. I. Cross. 



Notes on Comets and Meteors. J3y W. F. Dennino, 



F.R.A.S 



The Face of the Sky for March. By A. Fowleb, f.b.a.s.... 

 Chess Column. By C. D. Locock, b.a 



10 



5t 



55 



Cil 



C-J. 



r,:\ 



63 

 64 



(io 



6(5 

 6!l 



70 

 71 

 71 



EXPLORING THE THUNDER CLOUD. 



By the Rev. John M. Bacon', f.r.a.s. 



Pebchaxce you have Iain awake in a draiiglity seaside 

 lodging when the wind has been rising, and have heard a 

 door in the house banging at intei-vals at the sport 

 of the wind. Time after time it opens a little way and 

 remains ajar, perhaps for quite a considerable period, 

 when it abruptly " blows to " again. And this pro- 

 voking performance goes on indefinitely with persistent 

 monotony. The puffs of wind that are responsible for 

 this annoyance, if in an incipient state, will often be 

 found to recur with almost rhythmic regularity. The 

 same phenomenon is noticeable enough out of doors on 

 most days when wind is stirring, but being then less 

 obtrusive generally goes unheeded. 



Sometimes, however, the gusts will come on with such 

 impetuous force — like very explosions — that they cannot 



W ignored. The sailor at st\i calls them great guns, and 

 I ho sailor by sky also learns to take heedful count of 

 thorn. On a stormy day, during those ticklish few final 

 minutes when a balloon is being '' weighed " and adjusted 

 for the start, the heavy gusts that swcoj) past have to 

 be promptly met, and it is fortunate that their on- 

 slaughts are often sufllciontlv woll-tini(>d (o allow of their 

 being fully o.xpotteil. 



It is no uncommon ovent for a thunder storm to arrive 

 with one of these wilder squalls, and in this. case it is 

 well known that tho motion of the storm as a whole is 

 markedly slower than the average speed of the wind— - 

 very commonly a shallow one -which bears it. On 

 another occasion the cloud may bo found riding some 

 upper and contrary current, and under these circum- 

 stances gives apparent justification for tho popular saying 

 that " a tluinder storm will come up against the wind." 

 Once this last summer I chanced to bo aloft when a 

 disturbance of this nature was brewing, and was able to 

 note tho gathering of the storm from tho somewhat un- 

 common point of vantage fiirniihod by a free balloon. 

 July 27 last, was, at least for Newbury and twenty 

 niiles round, a day that was characterised by such well 

 marked regular gusts as I have referred to. It also 

 became a typical day of summer stornis, and it should 

 be mentioned that the nature of the weather indicated 

 the passage of a well pronounced " secondary," such as is 

 so commonly associated with thunder storms. It is fre- 

 quently asserted that a characteristic feature of such 

 storms is that the lower sweep of wind which circles over 

 the surface of the ground is very shallow, while at only 

 a moderate height overhead there may be a wholly 

 different drift. This at any rate was the state of affairs 

 as betrayed by the behaviour of tli(> storm I am able to 

 describe. 



Before leaving the earth I had entered certain memo- 

 randa in my note book, one of which runs thus:-—" All 

 through the day weather cocks have been pointing E., 

 while clouds estimated at 2,000 ft. altitude have been 

 scurrying in an opposite direction. The first thunder 

 storm broke over the town at 1 p.m. It was short> but 

 severe, the thunder as heard in the main street being as 

 deafening and prolonged as any that I can recall." 

 Another note is to the effect that the oncoming storm 

 approached from due south, and as it burst on our en- 

 closure set the balloon, already filled, spinning in a 

 direction contrary to that of clock hands. Several pilot 

 balloons, which were sent up through the afternoon, and 

 which became invisible before they had reached any great 

 height, went sometimes S.W. and sometimes W., and 

 seemed to hesitate between these two directions. 



At 5.15 wha), was apparently the clearing shower had 

 passed over, and the sky was seen everywhere cloudless 

 up to a great height, the wind on the ground dropping 

 shortly to almost a dead calm. Had any cloudlet been 

 left in evidence at a few hundred feet overhead, or had 

 we at this juncture sent up another pilot, the ascent 

 might have' been postponed, or at least the more ex- 

 perienced among us would have altered their opinion 

 about the " clearing shower." 



At 5.45 we cast off and leisurely took a N.W. direction 

 heading for Swindon, and thus proceeded till we had 

 covered rather more than a mile in distance, and risen 

 about 700 ft. Ill height. At this point we abruptly came 

 under the inHucncc of a well defined current which 

 diverted our course to that of the Kennet Valley, trend- 

 ing sensibly due west, and we closely followed up the 

 line of this valley for many miles. ^, . ^ 



In scarcely more than twenty minutes from the start 



