August 7, 1890] 



NATURE 



349 



5- — Records of Self-registering Instruments. 

 * An examination should be made of the records of 

 self-registering instruments within or near the disturbed 

 area— particularly of recording barometers, magnetic and 

 tidal apparatus— with a view to determine the effects of 

 the shock on these instruments, and also to ascertain by 

 their means the exact time of occurrence. 



While answers to any of the above questions would be 

 useful in the study of an earthquake, especial pains 

 should, if possible, be taken to determine accurately the 

 time at which the principal shock occurs. Immediately 

 it is felt, the time should be noted to the nearest second, 

 and written down at once, a few seconds (to be ascer- 

 tained by trial) being allowed for taking out the watch 

 and reading off the time. As soon afterwards as pos- 

 sible, the watch used should be compared with an accu- 

 rately regulated clock. But if this cannot be done, if the 

 record cannot be relied on as correct to within a small 

 fraction of a minute, a less close approximation cannot as 

 a rule possess much value. The chief use of such a 

 record is then to determine the epoch of the shock ; and, 

 in a matter of this kind, when two consecutive shocks in 

 a given district may be separated by an interval of 

 several years, a question of a few minutes, more or less, 

 is of very little moment. 



Next in importance to time-observations are those on 

 the intensity of a shock. Without the aid of delicate 

 instruments it is of course impossible to estimate the 

 intensity with accuracy. But good results have been ob- 

 tained by the use of a rough scale, according to which 

 the intensity is determined by its effect on men and 

 their dwellings. The following is the Rossi-Forel scale,i 

 which is widely adopted by Italian and Swiss seismo- 

 logists : — 



Rossi-Forel Scale of Intensity. 



I. Micro- seismometric shock : noted by a single seis- 

 mograph, or by some seismographs of the same model, 

 but not by several seismographs of different kinds ; the 

 shock felt by an experienced observer. 



II. Extremely feeble shock: recorded by seismographs of 

 different kinds ; felt by a small number of persons at rest. 



III. Very feeble shock : felt by several persons at rest ; 

 strong enough for the duration or the direction to be 

 appreciable. 



IV. Feeble shock : felt by persons in motion ; disturb- 

 ance of movable objects, doors, windows ; cracking of 

 ceilings. 



V. Shock of moderate intensity : felt generally by 

 everyone ; disturbance of furniture and beds, ringing of 

 some bells. 



VI. Fairly strong shock: general awakening of those 

 asleep ; general ringing of bells, oscillation of chandeliers, 

 stopping of clocks ; visible disturbance of trees and 

 shrubs : some startled persons leave their dwellings. 



VII. Strong shock: overthrow of movable objects; 

 fall of plaster ; ringing of church bells ; general panic, 

 without damage to buildings. 



VIII. Very strong shock: fall of chimneys, cracks in 

 the walls of buildings. 



IX. Extremely strong shock : partial or total destruc- 

 tion of some buildings. 



X. Shock of extreme intensity : great disasters, ruins ; 

 disturbance of strata ; fissures in the earth's crust ; rock- 

 falls from mountains. 



Results to be expected. — It may be useful, in conclusion, 

 to point out some of the results we may expect to obtain 

 from a systematic study of earthquakes in this country. 



The mere indication of the occurrence of a shock felt 

 at a given place on a given day is of service in the com- 



' Arch. desSc. phys. et nat., 3me pfer. t. xi. pp. 148-149; Fouqud "Les 

 Tremblements de Terre," p. 22 (footnote); BuU. del yule, ital., anno iv. 

 ('877), PP- 39-4C. 



NO. 1084, VOL. 42] 



pilation of earthquake statistics, and will tend to give 

 completeness to our seismic record. With the help of 

 such a record we can study the laws of the periodicity 

 and geographical distribution of earthquakes. The time 

 is past for drawing up chronological tables of shocks felt 

 over the whole earth ; but the importance of making our 

 records complete for a definite area of study is becoming 

 more and more evident. 



The accurate determination of the time of occurrence 

 in different places is of the very highest importance. 

 Such observations, if sufficiently numerous, will help us 

 in investigating the position of the area which constitutes 

 the epicentrum ; the way in which the vibrations are 

 propagated outwards from the epicentrum ; the velocity 

 of the earth-wave, and the laws according to which the 

 velocity varies with the distance from the origin. A 

 knowledge of the time will also determine the question 

 of the coincidence of shocks in distant areas, separated 

 by a region in which the shock is not felt at all, and of 

 other phenomena which may seem to be more or less 

 intimately connected with the earthquake. 



By a study of the intensity in the different parts of the 

 disturbed area, we are enabled to draw one or more iso- 

 seismal lines with a fair approach to accuracy. From 

 the form of these lines we can ascertain the approximate 

 position of the epicentrum; and, from the relative dis- 

 tances between consecutive pairs of such lines, we can 

 determine the way in which the intensity decreases as 

 the earth-wave radiates from the origin, and the relations 

 of this decrease with the form and geological structure 

 of the ground. 



The chief point to which our researches at present tend 

 is thus the discovery of the position of seismic foci. But 

 our ultimate object is something higher than and beyond 

 all this. With certain exceptions, the slightest earth- 

 quake that occurs must indicate the site and mark the 

 epoch of a step in the process of terrestrial evolution. 

 To determine the laws of seismic distribution in space 

 and time would therefore be to discover, in part, the laws 

 that regulate the development of the earth's great surface- 

 features. The study of earthquakes is fascinating enough 

 in itself, but it acquires a loftier significance when viewed 

 in its wider relations ; for through it we may press for- 

 ward to the solution of the great problem of geology — 

 the origin and growth of mountain-chains. 



THE HORNED DINOSA URS OF THE UNITED 

 STATES. 



IN vol. xxviii. of NATURE (pp. 439 and 515), an account 

 was given by Prof. Moseley of the magnificent skele- 

 tons of Iguanodons now mounted in the Brussels Museum 

 of Natural History, which were at that time regarded as 

 among the most remarkable of that extinct group of giant 

 reptiles commonly known as Dinosaurs. Since that date, 

 however, we have been gradually— thanks to the inde- 

 fatigable labours of the transatlantic palaeontologists — 

 acquiring a fuller knowledge of the representatives of this 

 curious group, of which the remains are preserved in such 

 fine condition in the Secondary rocks of the United 

 States Within the last few years, from the writings of 

 Profs. Marsh and Cope — and more especially the excellent 

 figures by which those of the former are illustrated — we have 

 acquired so much information as to the form and structure 

 of the gigantic Jurassic species belonging to the Sauro- 

 podous sub-order of the Dinosaurs — such as Brontosaurus 

 — that we have begun to regard these extinct creatures as 

 old friends (or should we rather say enemies?) and to flatter 

 ourselves that our knowledge of the whole class is well 

 nigh complete. 



Recent discoveries in the topmost Cretaceous or Laramie 

 deposits of North America have, however, brought to light 

 the existence of a group of Dinosaurs, hitherto only very 

 imperfectly known, which are remarkable, not only on 



