June 29, 1899] 
slow but intermittent growth or extension of faults. This 
done, he draws on a map isoseismals or curves surround- 
* ing all places at which the intensity of the movement, as 
and Gloucester. 
represented in certain cases by its destructivity, has been 
approximately equal. The most important of these is 
isoseismal number 8, which is the innermost and 
contains some seventy-three places at which there was 
structural damage. It is oval or elliptical in form, with 
its major axis forty-three miles in length running from 
N.W. to S.E., and encloses the towns of Hereford, Ross 
Outside this are the isoseismals 
numbered 7, 6, 5 and 4, a series which become more and 
more circular in form, the latter extending beyond 
Wexford and Dublin in the west, and Norwich on the 
east. 
From the form of these isoseismals, especially that of 
No. 8, which is the most important, by reasoning familiar 
to seismologists it is shown that the disturbance origin- 
ated along a line of fault which dips to the north-east, 
and has a strike coinciding with the major axis of the 
& 
? 
innermost of these curves of equal intensity. 
It appears that two series of vibrations were noted, 
which at different places were different in intensity and 
duration. An examination of the records relating to 
these leads to the conclusion that the principal shock 
originated from two foci along the line of fault, one near 
to Hereford, and the other near to Ross. 
At this point Dr. Davison is hand in hand with the 
geologist who, having already mapped faults bounding 
the triangular area of May Hill, south-east of Hereford, 
now sees that there are good reasons for supposing that 
one of these is but the south-eastern extension of that 
revealed by the distribution of vibrational effects ac- 
companying the Hereford earthquake. Davison’s fault 
therefore throws new light upon the geotectonic relation- 
ships amongst the older rocks in Western Britain, and 
that there is such a rupture in the Old Red Sandstone 
to the east of Hereford may at any time be of 
importance not only to the geologist but to the engineer. 
Another set of lines discussed are those passing 
through places at which the same phase of the earth- 
quake was felt at the same instant. These are the well- 
known coseismal lines, which are less elongated than the 
isoseisinals, but have their major axis in approximately 
the same direction. From the distances between them, 
velocities of transit varying between 2814 and 3095 feet 
per second are calculated, suggesting, but not on very 
certain grounds, an apparent increase in the velocity of 
earthquake transmission as it radiates. With a know- 
ledge of the velocity between any two coseismals and 
the distance of one of them from the epicentre, the time 
of origin of the earthquake is determined as having been 
at 5h. 31m. 45s. a.m. 
To the seismologist, the most striking feature in Dr. 
Davison’s work is his treatment of the sound phenomena. 
Mr. Mallet in his classical work on the Neapolitan earth- 
_ quake of 1857 gives us a chapter on the sounds that 
‘the rending of rocks. 
attend a shock, and which are produced by steam or by 
In a previous publication, Dr. 
Davison has given us his views as to the origin of 
earthquake sounds, which he attributes to the slipping 
or mechanical disturbance in the marginal region of the 
seismic focus. 
NO. 1548, VOL. 60] 
NATURE 
195 
In the present work, he gives us a map showing 
isacoustic lines or lines of equal sound intensity. Any 
one of these lines passes through districts in which the 
percentage of observers who noted a sound are equal, 
and they are therefore more strictly speaking, as the 
author states, lines of equal sound audibility. 
The major axis of these closed curves is, roughly 
speaking, at right angles to that of the iso- and co- 
seismal curves. More accurately it is a hyperbolic trace 
which follows the band, along which it is shown that the 
two series of vibrations from the two earthquake foci are 
superimposed. 
The general result arrived at from the study of these 
isacoustic lines is that they confirm the conclusion that 
there were two distinct, or nearly distinct, regions along 
the fault line from which vibrations radiated, and that 
the slip at the northern end of this line occurred a 
few seconds earlier than at the southern end. In this 
discussion of sound phenomena we have something 
distinctly original. 
The shock was felt less upon hard rocks and on high 
ground than on soft ground and in valleys. In the 
Bangor-Anglesey district the shock was felt most power- 
fully upon the carboniferous and ordovician rocks, and 
less upon the volcanic materials and schists. It was 
felt underground in several mines; at some places it 
produced feelings of nausea, and many instances are 
recorded of horses, cows, dogs, sheep, pheasants and 
other birds having exhibited symptoms of alarm. 
Without going further into Dr. Davison’s work, taking 
the same asa whole, he is to be congratulated on having 
extracted from materials which at first sight are of very 
little promise a quantity of valuable and novel inform- 
ation. The Hereford earthquake was a transient shiver- 
ing of an exceedingly small portion of the earth’s crust ; 
and, considering that there may be 10,000 of these 
occurring every year, this one appears to have been 
more carefully studied than any of its predecessors of 
equal magnitude. 
Had the author contented himself with analysing half 
the facts he has collected, although the same would have 
made a column of print 100 yards in length, the prob- 
ability is that, beyond noting a number of incidents of 
local interest, our knowledge of seismic phenomena 
would have not been materially increased. As it is, 
especially perhaps with regard to isacoustics, a distinct 
advance has been made, and in the future we shall find 
others working on similar lines. J. MILNE. 
A BIOLOGICAL RECORD. 
L’Année Biologigue. Comptes rendus annuels des 
travaux de Biologie générale, publiés sous la direction 
de Yves Delage, professeur 4 la Sorbonne, avec la 
collaboration d’un Comité de Rédacteurs. Secrétaire 
de la rédaction, Georges Poirault, Docteur és sciences. 
Premiere année (1895). Pp. xlv + 732. | 1897. 
Deuxiéme année (1896). Pp. xxxv + 808. 1898 
(Paris : Schleicher Fréres.) 
eC one of the Woods Holl Biological Lectures, entitled 
“ Bibliography: a Study of Resources,” Dr. Charles 
Sedgwick Minot, himself the author of one of the standard 
zoological bibliographies, compares the biological biblio- 
