January 6, 1923] 
NATURE 33 

between the limits of 100 and about 180 or 200 km. 
radius. Confirmation of the existence of a “‘ Silent 
on ’’ was therefore once more obtained. Also, 
the times which the sound waves took to reach 
various distances are in most cases longer than they 
would be for normal propagation through the surface 
air. 
The accuracy of the time standard of the average 
non-scientific observer is not likely to be high, but 
when the British observations are classified with 
reference to apparent velocities of propagation, there 
> San to be some evidence that these tend to group 
emselves about points corresponding to velocities 
of 257. 335, 370, and Pag metres per second. The 
second group corresponds very closely to propagation 
through the aor ees gay Gea eiicrence being 
made for temperature and wind. In view of the un- 
certainty as to the accuracy of the observed times, it 
is doubtful whether the observations of the third 
group are to be regarded as truly distinct from those 
of the second, but it is just possible that this velocity 
is to be explained by the assistance of a strong north- 
easterly wind, and, though there is no actual measure- 
ment, it is not improbable that such a wind may have 
existed somewhere about the three- or four-kilometre 
level. At a height of one kilometre the mean wind 
over south-east England was north-easterly 15 m/s, 
and at a height of two kilometres E.N.E. about the 
same velocity. A ballon sonde reaching 9 km. in- 
dicated a resultant drift for the whole trajectory from 
about N.N.W., and a cirrus cloud observation obtained 
in Holland indicated an apparent velocity equivalent 
ra m/s from W.N.W. at a height of 10 km. 
special interest are the first and fourth groups 
with velocities centring at 257 and 508 m/s respect- 
ively. Five of the seven observations indicating the 
latter velocity were made at very considerable dis- 
tances from Oldebroek, namely at Newcastle, Bolton-le- 
Moors, Skipton-in-Craven, Northallerton, and Guern- 
sey. Prof. E. van Everdingen is of opinion that such 
observations and the proven existence of the “’ Silent 
Region "’ afford very strong evidence of the co-opera- 
tion of the hydrogen atmosphere. The view that the 
appearance of silent regions is to be ascribed to a 
ge in the constitution of the atmosphere at great 
os, a was put forward by Von dem Borne in rgro. 
Making certain assumptions as to the constitution at 
t heights, he calculated that the shortest possible 
istance at which sound rays, curved back by this 
high atmosphere, could reach the surface was 114 km., 
the ray becoming horizontal at a height of 75 km. 
Actually no case of so short a distance has yet been 
found. In 1915 van Everdingen, taking Wegener's 
hypothesis as to the occurrence of geocoronium in the 
eee and his percentage values as to constitu- 
tion, showed that it gave no betteraresult. On testing 
various hypotheses, the best results appeared to in- 
dicate a percentage of hydrogen at surface level of 
0-0001. 
In addition to the observations discussed above 
collectively, certain special observations were made in 
this country. The Acoustical Research Section of the 
Signals Experimental Establishment contributed most 
uable records obtained by means of hot wire 
microphones at Woolwich and at Biggin Hill, Kent. 
These were described and discussed in detail by 
Major W. S. Tucker in a ig ae to the Royal Society 
of Arts on November 29. In the case of the Biggin 
Hill record he attributes the first effect (indicating a 
velocity of nearly four times that of sound in air) to 
Li 3 through the water and the ground. 
At Eskdalemuir Observatory at 17 h. 29 m. G.M.T. 
a small upward movement of about one-thirtieth of 
a millibar on the microbarograph record was followed 
about 13 minutes later by an approximately equal 
NO. 2775, VOL. 111] 
one in the opposite direction. On the traces of the 
other instruments, including the seismographs, no 
evidence of an explosion effect is to be found. Mr. 
J. J. Shaw (West Bromwich) could also find no 
evidence on his seismograms, but stated that at the 
critical time many thousands of pedestrians and heavy 
vehicular traffic (the returning crowd from a football 
match) were passing his house. 
The collected observations of the various European 
countries are now being investigated by Prof. van 
Everdingen of the Dutch Meteorological Service. 
University and Educational Intelligence. 
AmonG University Extension agencies the Summer 
School plays an increasingly important part. This 
year eleven universities and university colleges in 
Great Britain were responsible for at least fifteen 
summer schools, not counting those organised by 
joint committees for tutorial classes in connexion 
with the Workers’ Educational Association. In 
the United States, summer courses are provided in 
numbers and on a scale far in excess of anything that 
has been attempted elsewhere. The Bureau of Educa- 
tion, Washington, has published a Bulletin on the 
subject (1922, No. 31) in which are shown the student 
enrolments in last year’s summer schools of the twenty- 
seven universities and colleges which sent representa- 
tives to the meeting of the Association of Summer 
School Directors. The largest were: Columbia 11,809, 
Chicago 6458, California 6176, Wisconsin 4547. Four- 
teen other institutions had enrolments exceeding 1000 
each. On the other hand, many of the best known, 
including Yale, Princeton, Vassar, and Brown, do not 
receive summer students: Yale experimented with 
the system for three years and then gave it up. 
Some of the most conservative colleges, while not 
undertaking summer schools of the ordinary type, 
have opened their doors in the summer for conferences 
and for special classes designed to establish contact 
with industrial workers. Many hesitate, as do uni- 
versities in this country, to increase their commit- 
ments in this direction for fear of financial difficulties. 
State universities regard the matter in a different 
light, and find that this and other forms of extension 
work help to justify in the eyes of the taxpayers their 
large demands on the public purse. In general the 
courses are devoted principally to the liberal arts and 
sciences and to education, but some schools of law, 
medicine and dentistry offer courses which count for 
their degrees, and in a few institutions engineering 
and architecture courses are provided. 
From the Royal Technical College, Glasgow, we 
have received a copy of their annual report on the 
work of the session 1921-22. Owing to the cessation 
of special classes held at the request of the Ministry 
of Labour under their ‘‘ Interrupted Apprenticeships " 
Scheme, the number of students was slightly lower 
| than in 1920-21, but compared with 1913-14 the 
year’s enrolment shows an increase of 150 per cent. 
he research work carried on in the college is extend- 
ing rapidly in volume and importance, especially in 
chemistry, metallurgy, and engineering. Much of 
it is undertaken at the instance of industrial research 
associations by the associations’ own workers under 
the supervision and guidance of the professors 
concerned. The course for the diploma in chemistry, 
recently extended from three to four years, includes 
in its final year three months devoted to experimental 
inquiry, on which a thesis is required to be written. 
This plan has been an unqualified success, the report 
says, from an educational point of view, and some 
of the theses presented last year were of such intrinsic 
