Jtaie 12, 1884] 



NA TURE 



149 



for hunting this species were yearly despatched. The 

 Americans called it " black whale," a denomination which, 

 by the bye, also applies to other kinds. 



Its range on the shores of America seems to have fallen 

 a little south of that of Europe. It is in fact most pro- 

 bable that the whale visited the coast of Florida during 

 the winter months, perhaps even more southern latitudes. 

 Northwards it might be found as far as the sea is free 

 from ice, but several circumstances seem to indicate that 

 it preferred a temperate zone, and that its appearance on 

 the shores of Greenland were merely migratory visits 

 during the hot season. It may in fact be assumed that 

 the North Cape whale made its regular migrations like 

 the Greenland whale ; in support of which I may point 

 out that from the thirteenth to the fifteenth centuries the 

 whale-hunting in the Bay of Biscay was carried on only 

 during the winter months, and around America was limited 

 to the season between November and April, at all events 

 on the coast of New England. 



What is known as to the principal haunts of this spe- 

 cies of whale is alone based on the reports we possess of 

 its hunting in the preceding centuries. 



From the eighteenth century we hear no more about 

 the catching of the North Cape whale in European 

 waters, and in the beginning of the present century it 

 also ceased to be hunted on the shores of America in 

 consequence of its great scarcity. 



It is therefore exceedingly interesting to find that the 

 North Cape whale is again appearing on the east coast 

 of America in such numbers that its catching is being 

 resumed. 



On the coasts of Europe the whale has only been dis- 

 covered twice during this century, viz. in 1S54, when a 

 young one was caught at Pampeluna, the mother escap- 

 ing ; and in 1877, when the carcass of one — thirty-six 

 feet in length — was cast ashore in the Bay of Toronto 

 in Southern Italy. The skeleton of the former was 

 brought to Copenhagen by the late Prof. Eschricht, where 

 it now is. 



The discovery which I made in 1882 on the shores of 

 Finmarken of remains of this species of whale, hunted 

 there by the Dutch in the sixteenth century, gave rise to 

 further investigations as to the probable reappearance also 

 in these parts of the North Cape whale, and from reports 

 and circumstances brought to my knowledge, I feel con- 

 vinced that considerable numbers of the North Cape 

 whale again yearly appear on the coast of Northern Nor- 

 way, where they were once so common. I must indeed 

 regret that to ascertain with positive certainty whether 

 this is a scientific fact is very difficult for a scientist whose 

 stay in a certain part for scientific research is limited to a 

 month or so. I hope, however, to obtain substantial proof 

 of my belief at no very distant date. 



For a figure of the North Cape whale I may refer the 

 reader to that published in May 1883 in the Bulletin of 

 the American Museum of Natural History, New York. 



The University, Christiania G. A. Guldberg 



MEASURING EARTHQUAKES 



I. — Methods 



T T is difficult to define the word earthquake in terms 

 *■ which will not cover cases to which the name is inap- 

 propriate. To say that an earthquake is a local disturb- 

 ance of the earth's crust, propagated by the elasticity of 

 the crust to neighbouring portions, is true, but the defini- 

 tion does not exclude, on the one hand, such tremors of 

 the soil as are set up by the rumbling of a carriage, by the 

 tread of a foot, or even by the chirp of a grasshopper, nor, 

 on the other, those slow elastic yieldings which result from 

 changes of atmospheric pressure, from the rise and fall of 

 the tides, and perhaps from many other causes. One 



writer, in his definition of the word, limits the name 

 earthquake to disturbances whose causes are unknown — a 

 course open to the obvious objection that if the study of 

 earthquakes ever advanced so far as to make the causes 

 perfectly intelligible we should, by definition, be left with 

 no earthquakes to study. It must be admitted, however, 

 that in the present state of seismology this objection has 

 no force, for in assigning an origin to any disturbance likely 

 to be called an earthquake, we have, so far, been able to 

 do little more than guess at possibilities. The more prac- 

 ticable task of determining what, at any one point within 

 the disturbed area, the motions of the ground during an 

 earthquake exactly are has lately received much attention, 

 and in this department of seismology distinct progress 

 has been made. 



Apart from its scientific interest, this absolute measure- 

 ment of earthquake motion is not without its practical 

 use. Though the recent sharp earthquake in the Eastern 

 Counties has reminded us that no part of the earth's sur- 

 face can be pronounced free from liability to occasional 

 shocks, these occur so rarely in this country that English 

 builders are little likely to let the risk of an earthquake 

 affect their practice. If Glasgow or Manchester had 



Fig. I 



been shaken instead of Colchester, the chimneys of the 

 mills would, we suppose, have risen again in a few weeks 

 no less tall than before. The case is different in an 

 " earthquake country," such, for example, as some parts 

 of Japan, where the present writer had the good fortune 

 to experience, during five years, some three hundred 

 earthquakes. Where the chances are that a structure will 

 have to stand a shock, not once in a few centuries, but 

 half-a-dozen times a month, the value of data which will 

 enable an architect or engineer to calculate the frequency 

 and amplitude of the vibrations, and the greatest probable 

 rate of acceleration of the earth's surface, does not need 

 to be pointed out. 



To know how the earth's surface moves during the 

 passage of a disturbance we must obtain, as a standard of 

 reference, a " steady-point," or point which will remain 

 (at least approximately) at rest. This is a matter of no 

 small difficulty, for (as will be shown in a second paper) 

 the motions during any single earthquake are not only 

 very numerous but remarkably various in direction and 

 extent. Most early seismometers were based on the idea 

 that an earthquake consists mainly of a single great im- 

 pulse, easily distinguishable from any minor vibrations 

 which may precede or follow it. The writer's observa- 



