i August 2 2, 1889] 



NATURE 



593 



do the same with the second set. On subtracting these we can 

 see at once whether the head has grown in any direction. 



As an example, G. F. R., who was measured sixteen times, 

 gave the following mean values : — 



+0-03 



■o"i4 



The differences show the alterations occurring in twenty-five 

 months. 



I have calculated the other fourteen cases in the same way, 

 and find that if the growth in width of the whole fifteen be 

 added together, and the same be done with the length and 

 height, the totals are only 



+ 0*24 inch in width, 

 -056 inch in length, 

 -082 inch in height. 



The average period during which these changes took place was 

 thirteen months. 



These 107 measurements which I have discussed therefore 

 show a small dimimdion in the head capacity as the individual 

 grows one year older, but this is so small compared with the 

 probable error, that the observations are quite consistent with 

 the hypothesis that the head remains quite stationary. 



Ten measurements of the height of one individual, taken at 

 successive years from twenty to thirty, would give us a better 

 idea of the normal growth during that period, than many times 

 that number if each were taken on separate individuals, for the 

 range of individual variation at any age far surpasses the 

 amount of growth in any one of them. For the same reason I 

 think that the above 107 measurements made on fifteen indi- 

 viduals furnish a surer answer to the question, " Does the head 

 of a University student grow after the age of nineteen ? " than 

 ten times the number made indiscriminately, and simply grouped 

 by age. F. M. T. 



Trinity College, Cambridge, August 3. 



The Supposed Connection between Distant Earthquake 

 Shocks. 



It is very commonly assumed, whenever seismic disturbances 

 at different localities occur synchronously, that, however re- 

 motely they may be situated, there is necessarily a connection 

 of some kind between the shocks, originating in a common 

 cause. A forcible illustration of this fallacy, as I think, having 

 recently appeared in your columns, I beg to take this oppor- 

 tunity of questioning the position so generally adopted, and of 

 testing the validity of the involved theory of earthquake causa- 

 tion by the light of the evidence furnished in the concrete case 

 which has been presented in support of it. 



On April 18 a .somewhat remarkable earthquake took place 

 in Japan, at about the same time that some rather considerable 

 shocks were registered at. two seismic stations in Germany. 

 These occurrences were ably treated from the point of view 

 in question in Nature of July 25 (p. 294), by Dr. E. von 

 Rebeur-Paschwitz, of Potsdam, and argued to a final issue. 



It is taken for granted, primarily, under this hypothesis, that 

 every minor earthquake- shock at any given point is the effect, 

 direct or indirect, of some more violent disturbance elsewhere, 

 near or distant ; and it is further supposed that the latter is, in 

 its turn, a more direct result of a volcanic outburst at some 

 special centre of activity, known or unknown. From this pre- 

 mise it must be inferred that no micro-seismic shock can ever 

 take place otherwise than as a throw-off from some violent dis- 

 turbance more or less remotely located. When we examine 

 this conclusion, however, and consider more broadly the con- 

 comitant relations of earthquake phenomena, we shall, I think, 

 , find that it possesses no foundation whatever in facts, and that 

 the hypothesis does not bear the strain of such evidence as 

 may be adduced from recent observation. We know, for in- 

 stance, (l) that seismic activity is an experience of almost daily 

 frequency in some localities, as in Japan, obviously without 

 relation to the volcanic eruptions which occasionally take place 

 in near proximity ; (2) that, on the other hand, volcanic ex- 

 plosions sometimes occur unaccompanied by any widespread 

 upheaval or distant undulations ; and (3) that the earth's crust 

 is, moreover, subject to an apparently constant state of slight 



vibrations or micro-seismic prlpitition, in parts of the globe 

 where perceptible shocks are less commonly experienced. 



In the light of these facts the theory under discussion might be 

 readily disposed of as a foregone conclusion, but it will be more 

 satisfactory to prove its fallacy by means of the evidence afforded 

 by the earthquakes recorded in these pages as having taken 

 place at Tokio and in Germany on April 18, especially as the data 

 have been so completely recorded by Dr. von Rebeur-Paschwitz. 

 After considering the details registered by the seismometers 

 stationed at Potsdam and at Wilhelmshaven (distant about 220 

 English miles), he has applied himself to the problem of making 

 these facts fit in with the record of a shock which was ex- 

 perienced at Tokio at nearly the same time. It is to be 

 remarked that the only source of information respecting the latter 

 shock is the note which appeared in Nature of June 13 (p. 

 162), in which the information that a violent volcanic eruption 

 was taking place at Vries Island, "possibly 60 miles off," is 

 repeated from a note on the previous page where the island is 

 spoken of under its local name, Oshima. Dr. von Rebeur- 

 Paschwitz too hastily accepts the connection suggested, and upon 

 this slender basis rests his whole argument. 



Now it would certainly happen that any earthquake transmit- 

 ting i'.s effects to a locality on the opposite side of the earth 

 would affect also, in varying degrees, all the countries along the 

 line travelled by the seismic wave ; and that a constant diminu- 

 tion in its force would be a characteristic feature of such a 

 phenomenon. But what is the actual evidence in the case in 

 point ? We are told that at Tokio the maximum oscillation 

 registered was no more than about 17 mm., while at Potsdam 

 the greatest amplitude of oscillation is stated to have been 154 

 mm. The seismometers in use may possibly be different in type, 

 but there is surely not such great difference in construction as to 

 cause the complete reversal of the readings, as would be required 

 also by the accepted theory ; it may rather be accepted, no doubts 

 being entertained, that the resultant figures may be fitly com- 

 pared. But the conclusion arrived at is at once seen to be 

 absurd, for the lesser shock at Tokio could not possibly produce 

 the ninefold greater one in Germany ; while no mention what- 

 ever is made of any intermediate effects being produced along 

 the path of the wave. It is, moreover, especially stated (p. 163) 

 that this particular shock at Tokio was by no means a strong 

 one ; its "peculiarity lies, not in its violence, but in the extreme 

 slowness of its oscillations." Yet it is calculated by Dr. von 

 Rebeur-Paschwitz that the mean velocity of transmission of the 

 wave (occupying ih. 4"3m.) was " 2142 metres of propaga- 

 tion," which is really 167 metres above the mean of the different 

 rates computed by the two authorities cited. 



Again, the volcanic eruption of Oshima or Vries Island, at 

 about 60 miles distance from the main island, which is said to 

 have destroyed upwards of 300 houses, and killed 170 persons, 

 took place, not on the i8th, but on the 13th and 14th of April 

 (cf pp. 162 and 179, where fuller details are given). Besides 

 this difference in the dates, no exceptional earthquake shocks 

 are reported to have occurred at Tokio during the eruption, and 

 I fail to see the possibility of any connection between the two 

 particular phenomena considered. 



If there were any direct seismic connection between Japan 

 and Germany, the latter country would surely be subject to 

 regular transmissions of the shocks which prevail at Tokio. The 

 ample data furnished suffice to prove that it is not the case. We 

 are informed, in a postscript to the letter under consideration 

 (p. 295), that several other shocks were recorded at both Pots- 

 dam and Wilhelmshaven about this period, viz. on April 5, 8, 

 15, 28, and May 31 ; at Vo\.sda.m alone on April 25, May 21, 

 25, and 26 ; and at Wilhelmshaven two shocks were felt on May 

 30, " probably connected with the English earthquake of this 

 day." These various shocks were not experienced equally by the 

 instruments at the two stations, and they do not even seem to 

 have been necessarily connected throughout, for we are told 

 that on May 30 there was "perfect steadiness at Potsdam," 

 while four of the shocks mentioned were not felt at Wilhelms- 

 haven. 



It is curious to note that no connection is supposed in respect 

 of other earthquakes, and of volcanic activity in nearer prox- 

 imity in Europe, although several such occurrences have happened 

 during the same period. Thus, on April 26, several shocks were 

 experienced at Schaffhausen, &c. (Nature, vol. xl. p. 84) ; on 

 April 27, a "severe " one, lasting 4 seconds, was felt at Agram 

 (ibid. p. 45), a district much subject to seismic disturbance ; on 

 April 30, there was one along the coast of Norway (p. 1 33) ; and 



