144 



SCIENCE. 



[Vol. XIII. No. 316 



ifrom the centre. At Taggia it was twelve feet ; at Nice, fifteen 

 feet. 



In many places of the region where the earthquake displayed its 

 •greatest power, some observers claim to have heard a noise preced- 

 ing the motion. To some it seemed to be similar to the rattling of 

 a train ; but it is more generally compared to the howling of a hur- 

 ricane, or to the rattling of a cart rolling over a stone pavement, or 

 to distant thunder. Even in the third zone there are numerous 

 iplaces in which the noise was heard before or during the shock. 

 In the fourth zone it was noted in very few places. In several 

 places in the province of Porto Maurizio a subterranean noise was 

 all that was observed ; it was not followed by any movement. 



Great care was given to the determination of the direction of the 

 first shock. The methods applied were to inquire into movements 

 of lamps and other hanging objects, the stopping of pendulum 

 clocks, the removing or falling of objects, and the destruction of 

 buildings. This part of the investigation showed, that in the whole 

 region of the Ligurian Apennines, which was shaken most violently, 

 all directions were equally frequent. This fact suggests the e.xist- 

 ence of an elongated epicentre parallel to the Ligurian coast. East 

 ■of the meridian of Oneglia, directions between east-north-east to 

 west-south-west and north-east to south-west prevailed. West of this 

 meridian the greater number of waves were in the directions from 

 ■east to west and from south east to north-west. In many places 

 the direction of the movements changed once or twice during the 

 first shock. Thus movements resulting directly from the shock, and 

 secondary waves, could readily be distinguished. In many cases, 

 among the various directions, two were prevalent which were ver- 

 tical on one another. 



A remarkable phenomenon was observed in the valley of Padua. 

 The direction pointing towards the centre of the disturbance existed 

 •only during the latter part of the shock. In the beginning the crys- 

 talline rocks of the West Alps, which were shaken a few moments 

 'before the neighboring recent deposits, deflected the waves towards 

 the arc of the valley of Padua, giving them an east and west direc- 

 tion. 



If all important directions of shocks are marked on a map of 

 western Liguria, they will be seen to converge in the sea between 

 ■Oneglia and St. Remo about fifteen or twenty five kilometres south 

 ■of the coast. Therefore this is the probable place of the epicentre. 

 The same place results from a study of the isoseismic lines which 

 are concentric to a point twenty kilometres south of Porto Maurizio. 

 -A secondary centre seems to have been in the sea south of Nice. 



A comparison of the most trustworthy reports shows that the 

 Ligurian coast between Nice and Laona was struck by the great 

 shock at 6.20 A.M.: therefore the shock must have reached the epi- 

 centre a little before this time, probably at 6.19 A.M. If this move- 

 ment is considered the beginning of the shock, and the time of the 

 disturbances observed at other places is compared to it, it appears 

 that the velocity of transmission was not equal in all directions. 

 It was greater to the west, being 4,762 feet in the direction of 

 Marseilles and Nice, and only 1,916 feet in that of Genoa. This 

 ■difference is probably not real, as the first shock of Nice seems to 

 have originated at a secondary epicentre south of Nice, the exist- 

 ence of which was known through the earthquakes of 1564 and 

 1752. 



Only in a few places was it possible to ascertain the vertical 

 angle of the shock with any degree of exactness ; but the value of 

 40° seems to be well assured by observations between St. Remo 

 and Albenga. Based on these observations, and on the fact that 

 this angle decreased with increasing distance from the epicentre, 

 slower than it did in the great Andalusian earthquake of Dec. 25, 

 1884, the seat of the centre was found to be at a depth of eighteen 

 kilometres, while that of the secondary centre south of Nice was 

 somewhat less. It seems probable that the shocks preceding and 

 following the most violent one also proceeded from the main 

 ■centre, but that the first originated in a greater, the later in a less 

 depth. The centre seems to have approached the surface during 

 the seismic phenomena. 



The violent shock was felt at sea between Corsica and the west- 

 ern Riviera by several vessels, which were shaken in all directions, 

 the impression being that they had struck a rock. Almost every- 

 where on the Riviera the sea fell a little at the moment of the first 



shock, and suddenly returned to its former level, without the de- 

 structive waves which have followed other earthquakes. Some 

 observers maintain that the falling continued several days after the 

 earthquake, while at Laona and Porto Maurizio a change of level 

 is said to have taken place. No rise is said to have followed the 

 first fall. At Nice, St. Remo, and Savona dead fish were collected 

 after the earthquake. According to Bellotti, all of them were 

 deep-sea fish : therefore it cannot be doubted that violent shocks 

 occurred in considerable depths near the coast of Liguria. This 

 confirms the opinion that the centre must have been under the sea. 



The earthquake did not cause any important changes in the 

 topography of the affected region, and all of them must be consid- 

 ered dynamical effects of the tremors upon the surface strata 

 which were broken or slightly moved. None of the resulting 

 changes are connected with the prime cause of the earthquake. 

 No atmospherical phenomena proving the presence of an extraor- 

 dinary amount of atmospheric electricity were observed. In this 

 respect the Riviera earthquake differed from that of Andalusia. 



About nine minutes after the first shock a second one followed, 

 violent and long ; then at 8.53 A.M. (Rome time) a third one, short, 

 but almost as violent as the first, and very destructive in its effects. 

 Both these shocks were felt slightly in the whole region disturbed 

 by the first one. In the central zone about twenty-two shocks 

 more were felt in course of the 23d and in the following night. 

 Only one, at 2.20 P.M., was strong. After the 23d the number of 

 shocks decreased; but they continued until March 11, when the 

 most violent shock since the first three was felt. At Savona, be- 

 tween Feb. 23 and March 11, about fifty distinct shocks were felt. 

 Only the shocks of Feb. 23 were destructive. Six hundred and 

 forty persons were killed, and about as many wounded. The 

 damage in the province of Porto Maurizio is estimated at %2,- 

 600,000; in the environs of Albenga and. Savona, at $1,700,000. 

 No detailed estimates are available from the French districts. 



NATURE AND ORIGIN OF PHOSPHATE OF LIME.i 



The circumstances which have led to the preparation of the sub- 

 joined report on mineral phosphates are as follows : viz., in 1870 

 the present writer was employed by the superintendent of the Coast 

 Survey, the late Benjamin Peirce, to examine the phosphate beds 

 of South Carolina with a view to determining the limits of that 

 field ; it was also deemed desirable to ascertain, if possible, the 

 conditions which led to the formation of the deposits. 



It was at that time the intention of Professor Peirce to have the 

 geology of the belt of country within the limits of the Coast Survev 

 maps carefully determined, so that they might be shaped in a way 

 that would better serve the commercial interests of the country, 

 and also have a greater scientific value. After a time it appeared 

 that there were legal difficulties in the way of publishing these 

 studies in the reports of the Coast Survey, and this work was sus- 

 pended. It was the hope of Professor Peirce to secure a modifica- 

 tion of the law ; but before this was accomplished, he retired from 

 the post of superintendent, and his successor deemed it best to 

 abandon the project. During the two years in which I was en- 

 gaged in this work on the geology of the coast line, I became very 

 much interested in the problems connected with the origin and dis- 

 tribution of phosphatic deposits. From 1873 to 18S0, while em- 

 ployed as State geologist of Kentucky, I had a chance to see a good 

 deal of the somewhat phosphatic limestones of the Cambro-Siluri- 

 an sections, — a set of beds which, by their decay, have given great 

 fertility to the soils that lie upon them. The researches of Dr. 

 Robert Peter, the chemist of that survey, made it plain that the 

 phosphatic contents of the soils are among the first materials to be 

 exhausted by the careless tillage which characterizes our American 

 agriculture, and that they are the most costly to restore to the 

 soil. 



Extending the general inquiry to the grain-producing districts 

 which lie to the north and west of Kentucky, it became evident 

 that all those States which are now the granary of this country, 

 and the chief source of supply for European markets as well, are 

 rapidly exhausting their soils, and will soon be in grave need of 



* Portion of an introduction, by N. S. Shaler, to a forthcoming bulletin of the 

 United States Geological Survey, prepared by R. A. F. Penrose, jun. 



