424 
POPULAR SCIENCE REVIEW. 
that before them would have to he carried out before they found out their 
way. But every step taken was so much ground gained. Mr. Prestwick 
then showed how the ancient carboniferous formation had been disturbed, 
and compared all those that lay in a certain direction. Thus, in Belgium, at 
the foot of the Ardennes, there was a patch of coal-measures forty or fifty 
miles long, and running in an east and west direction. In Somersetshire 
the range of hills had the same direction as those of the Ardennes. The 
coal basin at the latter place had the same strike as those of Bristol and 
South Wales. The elevation of these took place before the formation of the 
new red sandstone. The present surface elevation was no guide whatever to 
the disposition of the ancient rock. In Belgium the coal dipped beneath the 
chalk, and the question was what became of it? If the strike always 
followed the same line there would be no difficulty in answering this, but 
it did not follow a straight line, but was curved, as in the Ardennes Hills. 
Mr. Godwin Austen thought that the Ardennes chain passed underneath 
where they stood, but Mr. Prestwick slightly differed from this, and 
thought the strike and range of the coal-measures in the South Wales coal- 
field and that of Belgium extended farther north. This was not an experi- 
ment to find coal, as had been asserted, but simply a scientific experiment 
to determine the position of the primary rocks. With other similar borings 
it might be possible to discern the actual range of the older rocks, and find 
out whether coal was to be found in Herefordshire or Kent. Where this 
boring was going on, they might meet with the mountain limestone, but 
he did not think the actual coal-measures would be found. If they came 
on the silurian rocks, they must go farther north to search for coal, so that 
it greatly depended on what they came to underneath them as to whether 
they should continue. 
MEDICAL SCIENCE. 
The Coagulation of the Bloocl . — A short communication on this point was 
made by Mr. E. A Schafer to the British Association, detailing a variety of 
experiments, from which the following conclusions were drawn: — That 
frog’s blood, especially if taken during the winter months, exhibits but very 
little tendency to coagulate, with the exception of the portion in immediate 
contact with a foreign surface ; that when apparently coagulated throughout, 
the central portions are very apt to remain fiuid, and to impart coagulability 
to the expressed serum ; that the clot, when formed, frequently tends to 
attain a relatively very small bulk ; and, finally, that this diminution in 
bulk is due to contraction merely — not reliquefaction of the fibrine. 
Rythmical Variation of Arterial Pressure . — Professor Burdon Sanderson 
read a paper on this subject at the same meeting as above mentioned. He 
pointed out the rythmical irregularities observable in the pulsation of cer- 
tain animals, stating that the periods of fast beating correspond to inspira- 
tion, and that the periods of slow beating correspond to expiration ; and 
explaining how this is recorded by a graphic method. Discussing the 
question of the relation of these phenomena, he showed that, when the 
muscles are subjected to paralysis, so that respiration almost ceases, there is 
