NATURE 



[January 20, 19 16 



VI. of the periodic table bein^^ followed by Nos. IV., 

 II., and zero, and then by Nos. VIu and Vh. 



In period VIb polonium appears to be the starting- 

 point of a new line, the thorium and actinium ele- 

 ments of which are still unknown. \o further pro- 

 ducts of Act C are known corresponding to the 

 polonium branch of the radium series, and ActC, 

 if it existed, should, by Fig. i, have the record range 

 of about 10 cm. About 0-17 per cent, of the ActC 

 rays are, however, said to have a range of 6-i cm., 

 which would be fairly suitable to an element of 

 at. wt. 206 on a line drawn parallel to the others on 

 Fig. I starting from polonium.^ 



It is specially noticeable that to make the actinium 

 points lie on the same lines as the corresponding 

 radium and thorium elements, its atomic weight must 

 be reckoned in every case from actinium = 222 instead 

 of 226. This means that the actinium series branches 

 olT from the uranium stock at Ur(2) instead of at 

 Ur(i). Either scheme is equally allowable, but no 

 evidence has hitherto been brought forward to decide 

 between them. 



Another set of lines can be drawn on Fig. i, one 

 through the actinium points, one through the thorium 

 points, and the lowest through the uranium elements. 

 The latter are, however, very scattered, and include 

 thorium itself amongst them. The lines do not go 

 beyond the " A " elements. 



These relationships were detected from noticing 

 first the evident family resemblance between the 

 y rays in the isotopic groups. For example, in period 

 IVb we have : — 



Among the ^ rays something of the sort is notice- 

 able, It. generally falling with increasing atomic 

 weight, but for the very soft (fi) rays /x is directly 

 proportional to the 33rd power of m. 



F. Gilbert Carruthers. 



December 14, 1915. 



The Naming of Earthquakes. 



An earthquake is usually distinguished by the name 

 of the town, province, or country, near or within which 

 it originates, and by its date — the double nomenclature 

 serving to determine its position in space and time. 

 With regard to the latter element, absolute uniformity 

 prevails. The )''ear, month, and day are always given, 

 except for great and long-past earthquakes, for which 

 the year only is sufificient. My object in this letter 

 is to suggest the desirability of similar uniformity in 

 the use of the place-name. 



Nearly all seismologists have a different standard 

 for earthquakes of their own country and for those 

 of distant lands. An Italian, for instance, will speak 

 of a Benevento earthquake or a Neapolitan earth- 

 quake, but also of an Indian earthquake, or even of 

 an Asiatic or Pacific Ocean earthquake. Temporarily, 

 no doubt, the use of the country's name is convenient; 

 but, as every country contains many seismic regions, 

 its continuance is undesirable. Even in the same 

 country various methods prevail. Thus, Indian seis- 

 mologists describe a Bengal, a Kashmir, and a Kangra 

 earthquake. 



1 With such a short ra-'ge of u> it is not ea«y to distinguish los w from a. 

 For convenience, a> and a are both shown on this scale, as well as log o and 

 loa a. 



2 The figure for lead is for the characteristic X-ray. 



NO. 2412, VOL. 96I 



These variations in nomenclature are clearly incoij 

 venient. On the one hand, different names are gtv«! 

 to the same earthquake. Thus, one may be call* 

 the East Anglian, the Essex, or the Colchester earth^ 

 quake ; another the Indian, the Assam, or the Calcutta^ 

 earthquake. On the other hand, the same name 

 applied to earthquakes with difTerent origins. In th^ 

 writings of Italian seismologists, the terms " Cals 

 brian earthquake" is of frequent occurrence. As 

 family or generic name it is useful, but it groups 

 together earthquakes which belong, as Dr. M. Baratta^ 

 has shown, to eleven different seismic zones. Thusl 

 the six great earthquakes of the Calabrian series of| 

 1783 affected in succession the Palmi, Scilla, Monte-'^ 

 leone, Messina-Scilla, Monteleone, and Girifalco zones^l 

 and might with advantage have been designated by' 

 their names. Again, the earthquake of 1638 occurred-; 

 in the Nicastro zone, that of 1659 in the Monteleone! 

 zone, that of 1836 in the Bisagnano zone, that of 1854 ' 

 in the Cosenza zone, that of 1894 in the Palmi zone, 1 

 and that of 1907 in the Gerace zone. These earth- ] 

 quakes, in like manner, might be named after the \ 

 corresponding zones. To this rule, however, there ; 

 must be occasional exceptions. For instance, the earth- > 

 quake of 1905 originated in five zones, and it would | 

 be out of the question to call it the Palmi-Monteleone- 1 

 Nicastro-Cosenza-Bisagnano earthquake of 1905.1 

 When the epicentre covers so large a part of a pro-j 

 vince, it establishes a claim for this earthquake to be,' 

 known as the Calabrian earthquake of 1905. '-\ 



While adhering so far as possible to prevalent cus-i 

 toms in naming earthquakes, and especially adopting! 

 those assigned to them by their principal investigators, \ 

 I would suggest that the choice of names should be; 

 determined by the following principles : — * 



(i) Old and obsolete names of districts, such as East ^ 

 Anglian, should be avoided, as conveying little or nda 

 impression of locality to foreign seismologists. \ 



(2) Names of valleys, hills, seas, lakes, or other; 

 physical features should not as a rule be used, with| 

 perhaps occasional exceptions, such as Exmoor or| 

 Ochil, when there are no prominent towns or villages S 

 in the neighbourhood of the epicentre. 



(3) Names of islands as geographical terms may,.! 

 however, be usefully employed when the islands are;^ 

 small (as Zante), or perhaps large and not well known' | 

 (as Formosa), but not w'hen they are large and well; 

 known (as Jamaica). Thus, it would be more con-J! 

 venient to speak of the Ischian than of the Casamic-'^ 

 ciola earthquake, and of the Kingston and Port Royal ^ 

 than of the Jamaica earthquakes. ' ■'% 



(4) Whenever possible, the name of a prominent or* 

 well-known town near the epicentre should be applied. I 

 The term Charleston earthquake, for instance, isi 

 more descriptive than the Woodstock-Rantowles earth-; 

 quake, though these places are much closer to the \ 

 double epicentre. j 



(5) If there is no large town near the epicentre, thei \ 

 name of a small town or village (with that of the,' 

 province or county added in brackets) may be usedl 

 with advantage, such as the Viggianello (Basilicata)'; 

 earthquake of 1894, or the Strontian (Inverness-shire) \. 

 earthquake of 1902. ,^ 



(6) When the epicentral area is of considerable size,. 5 

 the name of a single town ceases to convey the desiredSj 

 impression, and the names of many places would be"* 

 cumbrous. Thus, an earthquake with an epicentral * 

 area at least 290 miles in length deserves the name ) 

 of Californian rather than that of San Francisco. An j 

 earthquake which originates in five seismic zones, ' 

 which are often disturbed separately, is, as already ; 

 mentioned, suitably described as a Calabrian earth- i 

 quake. Charles Daviso.v. | 



16 Manor Road, Edgbaston, Birmingham. ^ 



