Fuly 30, 1885] 
NATURE 
299 
2 
altered rocks of the Ardennes; the Devonian limestones of 
Roly, &c., which M. Dupont regards as true coral atolls ; 
the grand section of Devonian and Carboniferous limestone 
along the Meuse ; the Grotto of Han, and the Deyonian lime- 
stones, &c., near Rochefort. The circular contains nine maps 
and cuts illustrating the geology of Southern Belgium, a table 
of geological formations, and a list of maps and books relating 
to the district. There are also full particulars as to routes, fares; 
&c. A pamphlet on ‘‘ The Geology of Belgium and the French 
Ardennes,” containing papers by Gosselet, Bonney, Rutot, Van 
den Broeck, and Topley, has also been prepared by the Asso- 
ciation, and is published by Stanford. This gives a fuller 
account of the literature, and is illustrated by three maps and 
thirteen cuts. 
On Saturday, July 25, a whole day meeting of the Essex Field 
Club was held at Witham and neighbourhood. The party, 
about sixty-five in number, was met at Witham Station by the 
Vicar, Canon Snell, and after being conducted over the church, 
an inspection was made cf the ancient earthwork surrounding 
the railway station. A piper on this camp, which is believed to 
have been constructed by Edward I., was communicated by Mr. 
F. C. J. Spurrel, who had prepared for distribution a number of 
printed copies showing the plan of the entrenchments. After 
lunch at the ‘‘ Spread Eagle,” Witham, an ordinary meeting of 
the Club was held for the election and proposal of new members, 
Prof. R. Meldola, in the absence of the President, taking the 
chair. At the conclusion of the meeting brakes were in 
attendance, and the party proceeded to Black Notley, passing 
en route through the village of Cressing, where in former times 
the Knight Templars had a preceptory. The remains of the 
Temple, now a farmhouse, were inspected by the permission of 
the present owner, Mr. J. H. Shoolbridge, who had had excava- 
tions made in various parts of the grounds in order to expose 
some of the old brickwork foundations. In the churchyard of 
Black Notley, by the tomb of John Ray, Prof. G. S. Boulger 
gave an excellent account of the ‘‘ Domestic Life of John Ray 
at Black Notley.” Mr. E. A. Fitch followed with an equally 
interesting account of Ray’s labours as an _ entomologist. 
The Rector of Black Notley, the Rev. J. Overton, was 
in attendance in order to conduct the party over the 
church. In the neighbouring school-room the Rev. F. 
W. Kenworthy, Vicar of Braintree, had arranged for 
exhibition a fine collection of flint implements, many of which 
had been found in the neighbourhood, and some of the palzo- 
lithic specimens being of special interest as having been found 
beneath the chalky boulder clay. After leaving the school-room 
a visit was paid to ‘‘ Dewlands,” the home of John Ray at 
Black Notley, by the permission of Mr. Mortier, the present 
occupier. Proceeding to Faulkbourn, the rector, the Rev. F. 
Spurrel, conducted the party over the church, and, by the 
invitation of Capt. Talbot, Faulkbourn Hall was next visited, 
although the length of the day’s programme prevented the club 
from taking advantage of the hospitality of the owner. Aftera 
short ramble through the grounds and an inspection of the hall 
from the exterior, the party proceeded to Terling Place, wherea 
most hospitable reception was given by Lord and Lady Ray- 
leigh. In the course of the evening Lord Rayleigh addressed 
the meeting on some mechanical questions involved in the flight 
of birds, and some of the party were then conducted to the 
laboratory, where a number of experiments bearing upon his 
lordship’s researches on sound, hydrodynamics, &c., had been 
arranged for exhibition, Amongst those present at the meeting 
were Mr. G. J. Symons, F.R.S., Prof. S. P. Thompson, Mr, 
E. B. Knobel, Sec. R.A.S., Dr. T. Taylor, &c. In carrying 
out the local arrangements much assistance had been rendered 
by Mr, W. D. Cansdale. 
Tue British Medical Association is holding its annual meeting 
this week at Cardiff. 
THE annual meeting of the Belgian Royal Society of Public 
Medicine, to be held at Antwerp on August 26-30, will this 
year assume a somewhat international character. The Com- 
mittee issue a special invitation to its foreign corresponding 
members, with a view to their taking part in the discussion of the 
main topic to be submitted to the meeting. That topic is thus 
formulated :—‘‘ What are, in the present state of epidemological 
science, the most practical international prophylactic measures 
to be taken, especially in Belgium, against pestilential malaria?’ 
THE annual meeting of the National Fish Culture Associa- 
tion will take place on Thursday next under the presidency of 
the Marquis of Exeter, when reference will be made to the 
Indian and Colonial Exhibition to be held next year, at which 
the Association is to represent the Fisheries Department, in 
accordance with the request of the Royal Commissioners. 
AT the last meeting of the Seismological Society of Japan 
(reprinted in the ¥apax Gazette) Dr. Knott read a paper on 
earthquake frequencies. The writer’s aim was to discover, if 
possible, some satisfactory reason for the winter maximum of 
frequency. Earthquake statistics show that, wherever there is a 
marked winter season there is a corresponding increase in 
seismic action. In searching for possible causes for this 
periodicity Dr. Knott left out of account purely terrestrial 
actions, due to the earth’s cooling and shrinking, or to the 
unequal distribution of surface matter as displayed in the 
arrangement of continents and oceans, for, although these no 
doubt produce earthquakes, they cannot cause periodicity. This 
restricts us to such periodic stresses as may result from the tidal 
actions of the sun and moon, or from the meteorological changes 
which accompany the sequence of the season. The writer dis- 
cusses each of these possible causes in turn. Earthquake sta- 
tistics do not afford ‘us any clear evidence of fortnightly or 
monthly periods, and on the whole he discards the tidal action 
of the sun and moon as incapable of explaining the annual 
period in earthquake frequency. Coming to meteorological 
causes, the seasonal changes of temperature cannot have any 
direct effect, as they are inappreciable at a depth of from 20 to 
30 feet ; storm depressions and wind generally may be left out 
of account, as the earth is sluggish in responding to short-lived 
stresses. The attempts that have from time to time been made 
to connect earthquakes with the indications of the barometer a¢ 
the locality could hardly be expected to lead to any definite 
result, for we have no right to assume that the earthquake is 
caused by an external stress applied directly at the origin of the 
disturbance. We must consider the stresses over a large area 
inclosing the locality in question. Are there, then, any meteoro- 
logical phenomena of the necessary period and sufficiently long- 
continued in their different phases to give rise to stresses to which 
the earth’s crust could reasonably be expected to yield? There 
seems, Dr. Knott says, to be such a possible cause in the annual 
oscillations of barometric pressure over land and sea. In cold 
weather this pressure is high over the land and low over the 
sea; in warm weather this relation is just reversed. This gives 
rise to steep gradients, which of course are steepest just where 
land and sea meet. Japan, for instance, between Siberia and 
the Pacific, is under one of these steep gradients. This semi- 
annual see-saw of pressure is very marked in all temperate 
regions, the steepest gradients always occurring in the winter 
months. Then, so far as regards the winter excess of pressure, 
a much more powerful cause than barometric changes is to be 
found in the snow-fall. If we consider the great winter 
accumulation of snow in the higher latitudes, especially over 
continental areas, such as Siberia, we see that the magnitude of 
the shearing stresses along the region where the snow accumula- 
