76 

the conclusions have been referred to in previous 
accounts of research work in this column. This re- 
port completes the first decade of operations on the 
mountain, and we are promised a brief outline of the 
work for this period. The past year is described as 
“one of the most productive of this period.”” We are 
told that solar research has progressed satisfactorily, 
that a beginning has been made in the application to 
solar phenomena of Stark’s capital discovery of the 
effect gf an electric field on radiation. One of the 
new conclusions in stellar astronomy promises to 
furnish the means of determining a star’s distance 
simply. by measuring its brightness and the relative 
intensities of certain lines in its spectrum. Labora- 
tory investigations and the work of construction have 
gone forward rapidly. With regard to the last-men- 
tioned, it is hoped to complete the dome for the 1o00-in. 
reflecting telescope next summer, and to set up the 
mounting in the autumn. The large mirror has 
already received an almost perfectly spherical figure, 
and preparations are being made for the work of 
parabolising it. The reader must refer to the report 
itself to note the progress made in the many and 
various investigations which are in operation, both on 
the mountain and at the base station. 
ANNUAIRE ASTRONOMIQUE ET M&TEOROLOGIQUE POUR 
1915.—The fifty-first issue of the useful handbook 
entitled ‘“‘Annuaire Astronomique et Météorologique ”’ 
has just come to hand. M. Camille Flammarion, the 
originator and editor of this handy reference book, 
has, in spite of the recent difficulties met with in 
Paris, produced the volume up to the high standard 
of its predecessors. Most of the readers of this column 
know the arrangement and subjects of the contents 
so well that it seems necessary only to direct attention 
to the issue of the volume. Nevertheless it may be 
added that under the heading, ‘‘ Scientific Notices,” 
which is an annual review of the progress of astro- 
nomy, the reader will obtain a good broad view of 
the year’s work, while in the numerous other sections 
dealing with the calendar, phenomena, astronomical 
tables, etc., illustrated by 120 figures of charts and 
diagrams, a mine of valuable material is included. 
THE AVEZZANO EARTHQUAKE OF 
JANUARY 13. 
pe most of the details contained in the present 
paper I am indebted to the courtesy of Dr. G. 
Martinelli, of the Ufficio Centrale di Meteorologia e 
di Geodinamico at Rome, and of Dr. G. Agamennone, 
the well-known director of the Geodynamic Observa- 
tory of Rocca di Papa, near Rome. 
The map of the isoseismal lines is a reproduction of 
that prepared by Dr. G. Martinelli from the numerous 
observations forwarded to the Central Office. The 
scale of intensity employed is that of the late Prof. 
Mercalli, which, in Italy, has superseded the Rossi- 
Forel scale. The degree X., for instance, represents 
the intensity of a shock capable of ruining many 
buildings and causing much loss of life; the degree 
VII. that of a shock that will throw down chimneys 
and produce slight cracks in numerous buildings; 
while the degree II. corresponds to a shock that can 
just be felt under favourable conditions by persons 
at rest. It will be seen that the isoseismal X. is an 
elongated curve including Avezzano at its western 
end. The isoseismal of intensity VII. is interrupted 
by the eastern coast of Italy, and extends beyond 
Rome to within a few miles of the western coast. 
The isoseismal of intensity IJ., which represents the 
boundary of the disturbed area, includes Parma, 
Mantua, Verona, and Venice to the north, and to the 
south approaches within thirty miles of Messina. 
NO. 2368, VOL. 95] 
NATURE 


[Marcu 18, 1915 

Thus the area disturbed is not less than 550 miles 
in length. Its width is, of course, unknown, but, if 
the mean radius be taken as 275 miles, the total dis- 
turbed area must extend over about 240,000 
square miles, an area about two-thirds of that shaken 
by the San Francisco earthquake of 1906. 
Dr. Agamennone informs me that the first vibra- 
tions were registered at the Rocca di Papa Observa- 
tory at 6h. 52m. 54s. a.m. (G.M.T.), but the vibra- 
tions soon attained such strength that the seismo- 
graphs there were thrown out of action. At Rome, a 
somewhat less sensitive seismograph registered the 
whole movement, though the pendular masses beat 
repeatedly against the screws which are arranged to 
protect the instrument from excessive oscillation. At 
Eskdalemuir, the first movement was recorded by the 
Galitzin seismograph at 6h. 56m. 45s., and the begin- 
ning of the principal portion at 7h. 1m., the instru- 
ment remaining in motion until 9h. 12m. Judging 
40 80) 120 
ILOMETRES. 















from the seismogram obtained at this observatory, the 
epicentre was at the distance of 1930 km. in the direc- 
tion 40° 50’ south of east; that is, in 42° N. lat., 
14° E. long. The centre of the isoseismal line of 
intensity X. is in 42° o’ N. lat., 13° 27’ E. long. 
According to a special seismological bulletin issued 
by the Georgetown (U.S.A.) University Department 
of Geology, the first tremors reached that place at 
7h. 28m. 4os., and the first oscillations of the principal 
portion at 7h. 36m. 4os. 
The Avezzano earthquake is noticeable for its extra- 
ordinary number of after-shocks. At Rocca di Papa, 
a sensitive microseismograph was at work again an 
hour after the principal shock, and, from January 
13-29, this instrument registered more than 500 after- 
shocks. That the earthquake was tectonic in its 
nature is indicated by the extensive disturbed area, 
the registration of the movement at great distances, 
and the unusual frequency of the after-shocks. 
