424 



KNOWLEDGE. 



XOVEMBEK. 191 I. 



of the instrument. Six-hour stars will be equalK" 

 easv, allowing, of course, for refraction, and the alter- 

 ation of eyepieces will be speedih' dispensed with. 

 Above all, the amount ot work done will be immensely 

 increased, and the comfort of an exactlv-adjusted 

 instrument the better appreciated. 



The larger the instrument the smaller the objects 

 attacked, and the more necessar\- the exactness 



required, since (iftentimes two or three douliles will 

 be found in the field, and to know one from the 

 other is hv no means easy. .\ little care thus 

 bestowed will be ampl\- rewarded, and the obser\er 

 will become the more satisfied with his hobby, and 

 instead of sclccfiiii; objects from Webb, will icork 

 tlimiii^h the book with ever-increasing satisfaction 



and delight. 



CORRESPONDENCE. 



THUXDERSTOKMS IN (iAKPlSSIO. 

 To the Editors of " Knowledge." 

 Sirs. — The fnllowiiT,; imti^ ;iiid accompanying sketches 



jr~?^ 



Figure 1. 

 Five long ribbons of Lightnins^. 



were made at Garessio. a small town in the Ligurian Alps. 

 about thirty kilometres inland from .Alassio. and at an altitude 

 of six hundred metres above the sea. 



The summer in that part of Italy has been a remarkable 

 one. not as has been the case in F.ngland and Northern 



F^IGURE 2. 



Mamillated cloud after a thunderstorm. loi:>kin,t; north. 

 August 29th. 1911. 1.0 p.m. Garessio, Italy. 



Europe, on account of the heat and drought, for our inaximnni 

 temperature never exceeded 29° C. (84 ■ 1 FM, and the first 

 part of the summer was so exceptionally wet that crops and 



flower gardens suffered greatly. The characteristic of this 

 summer which has made it a remarkable one was the 

 extraordinary pre\aleiice of thunderstorms, and the unusual 

 intensity of the electricity developed. There were thunder- 

 storms, either close at hand, or within visible and audible 

 distance, on twelve days in June. tweUe days in July, and 

 sixteen in August. 



In these storms, which usually culminated between one p.m. 

 and four p.m., the lightning was magnificent, ribbons of fire 

 running across the sky for miles, accompanied by a continuous 

 roar of thunder. Usually the flashes leapt from one towering 

 cumulus to another at an enormous height, and almost always 

 without rain. Only on one occasion was there a little 

 hail. I ha\e endeavoured to sketch one remarkable flash, 

 because neither I nor any of those who witnessed it can 

 recall ever having seen a similar phenomenon. The sky 

 had been dotted for several hours with curious irregular- 

 shaped cumuli of extraordinary hardness and compactness, 

 e\identlv highlv charged with electricity, and ascending 



W^^^jfc. 



-^n*- 



F^IGURE 3. 



Mamillateil cloud after a thunderstorm, looking south. 

 .Ans;ust 29th. 1911. 1.15 p.m. Garessio. Italy. 



in tall columnar masses much like the steam from a 

 locomotive's funnel. Suddenly one of these seemed to 

 become over-charged, and a violent and very rapid discharge 

 commenced, one flash of which I have endeavoured to depict. 

 (Figure 1.1 From a distinct centre of the cloud there burst 

 simultaneously five long ribbons of lightning, which traversed 

 a space of absolutely blue and cloudless sky. and ended 

 abruptly in the blue, as shown in the sketch. There was no 

 other cloud above or near the thundercloud, and the five 

 streams appeared all of equal length. The sun had recently 

 set behind the hills shown on the right, and the sky was still 

 luminous and blue. I have never observed such a thing before, 

 and should be interested to know whether it is a well-known 

 phenomenon — that is to say. the lightning travelling out of a 

 cloud into space and there terminating. 



The two other sketches I send because I remember seeing 

 a letter and illustration some time ago in " Knowledge." re- 

 cording a mamillated cloud. These mamillated clouds are not 



