124 



NATURE 



[September 30, 19 15 



the . other hand, the meizoseismal areas are much 

 elongated and their longer axes are directed roughly 

 towards the central crater and at right angles -to this 

 direction, implying that they are probably due to 

 slipping along radial and peripheral fractures (see 

 Nature, vol. xciii., pp. 272-3). 



The earthquakes of May, 1914, on the eastern 

 flank of Etna, supply useful evidence on this subject. 

 They have been studied with great care by Prof. 

 Gaetana Platania,^ who, with ample materials at his 

 command, confirms the conclusion arrived at in the 

 last-mentioned paper. Several of the shocks, besides 

 the principal earthquake of May 8, were of destructive 

 intensity, and the outer broken line on the accompany- 

 ing map includes all the places in which houses were 

 damaged by the different shocks. 



Slight earthquakes were felt within this area on 

 April 28 and 30, and May i and 2. The series proper 

 began on May 5. On May 7 at 5.35 p.m. (G.M.T.) 

 there was a strong double shock, the two parts being 

 separated by an interval of three to four seconds. In 

 the epicentral zones, indicated by the curves Nos. i 

 and 2, walls were cracked and some houses damaged. 



This may, as Prof. Platania suggests, have been a 

 twin-earthquake, but the evidence is insufficient to 

 decide the point. Soon afterwards, at 9 p.m., another 

 strong shock caused slight damage within the area 

 represented by the cui:ve No. 3. 



On the morning of May 8, only light vapours were 

 being emitted from the central crater of Etna and 

 from the vent on the north-east flank opened in May, 

 191 1. At about 5.30 p.m., however, extraordinary 

 activity was manifested in both, and this continued 

 for several days with a first maximum on the evening 

 of May 10, and activity above the average for the rest 

 of the month. 



Shortly afterwards, at 6h. im. 30s. p.m., occurred 

 the principal shock of the series, by which the towns 

 of Passopomo, Linera, Cosentini, Carico, and Mortara 

 were destroyed. The meizoseismal area is an elongated 

 ellipse (No. 4), about 6 km. long and 2 km, wide. 

 There was also a detached area of somewhat less 

 destruction (No. 5). Within the meizoseismal area 

 not only were the houses ruined, but the ground itself 



1 Sul periodo sismico del maegio 1014 nella regione orientale dell' Etna, 

 Plibl. deir Ist. di Ceorg. Fisici t Vnlcanologia della R, Universita di 

 Catania, No. 5, 1914. Pp. 1-48. 



NO. 2396, yoL. 96] 



was crushed. A slightly sinuous fracture traverses 

 the axis of this zone, as shown by the continuous 

 line in the map, and in its neighbourhood the ruin 

 was complete. Throughout its course there is almost 

 everywhere a change of level, in some places of a few 

 centimetres only, in others of as much as 40 centi- 

 metres or more, the ground on the north-east side 

 being depressed relatively to that on the south-west 

 side. There are also traces of a slight horizontal 

 displacement. 



Between May 8 and June 4 thirty after-shocks were 

 recorded, only one (that of May 28) being of any 

 importance. The meizoseismal area of this shock is 

 indicated by the curve No. 6. Prof. Platania notes 

 that there were other migrations of the epicentres 

 besides those noted above. He concludes that, during 

 this seismic period, the whole eastern flank of Etna 

 was disturbed, probably by subterranean movements 

 of the magma, which were responsible both for the 

 increased activity of the volcano and for the slips along 

 radial fractures which resulted in the earthquakes. 



C. Davison. 



METEOROLOGY WITHOUT 

 INSTRUMENTS.^ 



THOSE who have been compelled to wade through 

 the long-continued record of meteorological 

 observations know and dread the serried columns of 

 figures that tell of the scrupulous care with which the 

 conscientious observer has read his barometer and 

 thermometer. As a rule, it is impossible to inspire 

 the mechanical and lifeless record of the weather" of 

 the past year, or of the past decade, with any lasting 

 interest, but Mr. Backhouse, departing from stereo- 

 typed methods, has given us a book on climatology 

 that does not weary by its monotony or tire by its 

 endless repetitions. 



Much of the success and charm of this volume 

 depends upon the fact that it is a human document, 

 recording what has been seen and experienced, not 

 what is automatically registered by ingeniouslv de- 

 vised instrumental methods. It is a revelation of 

 character as well as an inquiry into the variation of 

 climatic factors. This record goes back to the time 

 when the author was a schoolboy at York, and de- 

 monstrates the value of habits of accurate and intelli- 

 gent observation, diligently preserved through life. 

 With perseverance and practice has come an acuteness 

 of perception that has made Mr. Backhouse one of 

 the most successful observers of those minute differ- 

 ences in the appearance of the sky or of the atmo- 

 sphere that escape untrained observers, who prefer to 

 consult the barometer rather than natural phenomena. 

 And with the increased capacity for observation has 

 come apparently the greater opportunity for exercising 

 it. To most people, the observation of such pheno- 

 mena as lunar rainbows or parhelia is a rare event, 

 and without such a trustworthy record as we have 

 here, many would be inclined to doubt their frequency. 

 Take again such instances as the successive alterna- 

 tion in the wind direction, known as " land and sea 

 breezes." Although the cause is operative all over 

 the world, we have come to regard these winds as 

 confined mainly to a few tropical localities, and be- 

 lieve that it would be vain to attempt their observation, 

 except in these favoured spots. But Mr. Backhouse 

 shows how the attentive observer can study the be- 

 haviour of these alternating breezes on our own coast, 

 and even mark the varying direction, as the azimuth 

 of the sun, at rising and setting, changes at different 



1 Publicationi of West Hendon House Observatory, Sunder'and. No iv. 

 Meteorological Observations, chiefly at Sunderland. By T. W. Backhouse. 

 Pp. v+t83. (Sundfrland : Hills and Co., 1915.) 



