278 



NA JURE 



\Jan. 22, 1885 



the Spanish Natural History Society of January 7, 1S85, has 

 been forwarded to us from Madrid for publication : — Mr. 

 Joseph Macpherson made the following remarks on the earth- 

 quakes in Andalusia : — " The earthquake which took place in 

 the peninsula on the night of December 25 last, and which can- 

 not yet be said to have ceased, has assumed a character of such 

 intensity, and presents in its action such marked coincide ces 

 with the geological structure of this part of the world, that I 

 think it will be interesting to enter into some detail with regard 

 to the principal conclusions to be deduced from that phenome- 

 non. Taking the whole peninsula, the disturbance may be 

 divided off into three successive phases, viz. : one of relatively 

 slight importance which occurred in the early morning of 

 December 22, and which was confined to the western portion of 

 the country, its effects being felt only in Galicia and Portugal ; 

 another, of the highest importance, which occurred three days 

 later, namely, at 9 p.m. on the 25th of that month; while the 

 third phase includes the oscillations which have taken place, and 

 are still taking place, in the districts most severely affected by the 

 earthquake of the 25th That earthquake extended over a very 

 considerable surface, the district affected to an appreciable degree 

 including approximately, it would seem, the whole country lying 

 between Cadis and Cape de Gata and between Malaga and the 

 Carpathian range. According to all the data known to us so far, 

 the oscillations gained in intensity as they proceeded southwards 

 from those mountain ranges, reaching their maximum of motion 

 in the region lying between the mountains of Ronda and the 

 Sierra Nevada. The shock was quite perceptible at Madrid, 

 where it was strong enough to stop a few clocks and ring a lew 

 belb. The movement was apparently that of a pendulum, and 

 its direction was from north to south Two successive oscilla- 

 tions were observed separated by an interval of from three to 

 four seconds, and each oscillation lasted from two to three 

 seconds. The movement gained in intensify, as I have said, as it 

 proceeded southwards, more especially after leaving the s mthern 

 border of the central tableland limited by the fault of the valley 

 of the Guadalquivir. Now, the interest of the phenomenon lies 

 in the coincidence observable between its various manifestations 

 and the geological structure of the peninsula. To make this 

 cleir, let me be permitted to offer a few observations on the 

 subject of that geological structure. The archaic formations of 

 the peninsula, with rare exceptions, lie in folds and faults 

 running with singular consistency from south-west to north-east, 

 and as an instance of this peculiarity I may mention the Car- 

 pathian range, which crosses the peninsula from east to west. 

 After these archaic disturbances the Cambrian and Silurian 

 deposits were likewise in their turn crumpled up into folds. 

 These, however, run from north-west to south-east, that is to say, 

 in a direction which forms almost a right angle to the earlier 

 archaic folds. Concurrently with this general crumpling of the 

 lower Palaeozoic strata, there appeared in a broad zone great 

 ui ses of granite, porphyry, diabase, and other kinds of rocks, 

 which cross the peninsula from Galicia to the valley of the 

 Guadalquivir, and which, geologically speaking, divides the 

 peninsula into two distinct parts. This huge belt, which may 

 be regarded as one of the most striking features of the 

 peninsula of our day, cuts and divides the archaic forma- 

 tions, as this may be perceived at once in the central Carpathian 

 range itself, which is interrupted between the Siena de Gata 

 and the Estrella range in Portugal. A study of the Mediter- 

 ranean watershed of Andalusia will show the existence of two 

 great mountain masses, chiefly formed of archaic deposits. One 

 of these is known by the name of the Serrania de Ronda, and 

 the other by that of the Sierra Nevada. Both run in a series of 

 folds and faults from south-west to north-east, and between 

 them there lies an interval filled up with palaeozoic, secondary, 

 and tertiary deposits. Towards the middle of this interval there 



rises up, like an island in the midst of these later deposits, a 

 series of ridges running from north-west to south-east, and 

 formed of archaic rocks. They are known by the name of the 

 Sierra Tejea and Sierra Almijara, and the folds of these rm^'\ 

 as in the case of the other archaic formations, run from south- 

 west to north-east. It is clear, therefore, that this intermediary 

 mountain mass is a segment "f a more considerable archaic 

 formation, separated from adjacent rocks through the sub- 

 sidence of the ground on both sides. Owing to constant oscil- 

 lations, this detached portion has been covered with the thick 

 mantle of sediment which now overlays it, and its structure is 

 easily accounted for as the resu't of that great fracture which 

 crosses the peninsula from north-west to south-east, in the pro- 

 longation of which lies the region I am now describing. This 

 fracture does not evidently end in the valley of the Guadalquivir, 

 and though the surface be covered over by later deposits, it 

 apparently extends to the country lying between the archaic 

 mountain masses of the Serrania de Ronda and the Siena 

 Nevada, which it divides from one another, and whose ancient 

 unity is testified by the Sierras Tejea and Almijara. The two 

 principal coincidences observable beUv een the phenomena of the 

 earthquake and the geological structure of the peninsula are: — 

 (1) That the disturbance of December 22 was confined '.'■ the 

 regions lying to the west of the zone above described ; an 1 (2) 

 that the most violent shocks of the earthquake of December 25 

 were experienced in the region intervening between the Sierra 

 Nevada anil the Serrania de Ronda, and precisely on the very 

 belt which incloses the archaic mountain mass of the Sierras 

 Tejea and Almijara. Th.it part of Andalusia, broken and torn 

 by the secular disturbances of our globe, has proved naturally 



the weakest, and has. therefore, been the most ex] .-d 



to the shocks from which Andalusia has so terribly suffei I. 

 There stood Albania, now prostrate in the river bed ; there, 

 Periana, a heap of ruins 3 m. high ; there Albunuelas, which 

 exists no longer ; there Zafarraya, Xerja, Torrox, and many 

 other towns and villages ; all testifying to the fragility of those 

 faults, which though dating back to the Silurian period, are 

 still apparently not completely welded. 



Mr. G. Johnstone Stoney, F.R.S., Vice-Presidei ol the 

 Royal Dublin Society, will give a discourse at the Royal Insti- 

 tution on Friday evening, February 6, on "How 'I!" i 

 presents itself in the Phenomena of Nature" ; and on the fol- 

 lowing day (Saturday) he is to begin a course of three lectures 

 upon the " Scale on which Nature works and the Character of 

 r her Operations." The following are the titles of tbe 

 three lectures : — " Operations of Nature carried out 'n a Great 

 Scale" ; "Operations which go on between Molecules " ; ami 

 "Operations which go on within Molecules, and the more Sub- 

 tile Operations of Nature." 



ACCORDING to Science, about 10 per cent, of the plants col- 

 lected in the North- Western Mexican States by recent collectors 

 prove to be new species. 



May we suggest to tli auth . :s of the British Mmeum the 

 desirability of taking some means of letting the public interested 

 in the matter know some little time beforehand when those lec- 

 tures are to be delivered which are so regularly reported in the 

 Times, but of the arrangements for which no one seems to know 

 anything ? 



Dr. ]. A. Fl I.Ming is about to give, at University College, 

 Gower Street, a course of lectures on " Mo I. in Applications of 

 Electricity in the Arts." The lectures will be interspersed with 

 practical demonstrations. 



The Electrical Exhibition, which was to take place at the 

 Paris Observatory in the beginning of January, has been post- 

 poned to March 19. 



