44 
certainly not the case. Usually there is no silent area. Again, 
although according to the analogy of Lloyd’s bands there might 
be a dark or silent place at a particular height above the water, 
say on the bridge of the Zvene, the effect should be limited to 
the neighbourhood of the particular height. At a height above 
the water twice as great, or near the water level itself, the sound 
should be heard again. In the latter case there were some 
difficulties, arising from disturbing noises, in making a satis- 
factory trial; but asa matter of fact, neither by an observer up 
NATURE 
the mast nor by one near the water level was a sound lost on | 
the bridge ever recovered. 
The interference bands of Fresnel’s experiment may be 
imitated by a bifurcation of the sound issuing from A (Fig. 1). 
For this purpose a sort of T-tube is fitted, the free ends being 
provided with small elliptical cones, similar to that already 
described, the axes of which are parallel and distant from one 
another by about 4ocm. The whole is constructed with regard to 
symmetry, so that sounds of equal intensity and of the same phase 
issue from the two cones the long diameters of which are vertical. | 
Ifthe distances of the burner from the mouths of the cones be pre- | 
cisely equal, the sounds arrive in the same phase and the flame 
flares vigorously. If, as by the hand held between, one of the 
sounds is cut off. the flaring is reduced, showing that with this 
adjustment the two sounds are more powerful than one. By an 
almost imperceptible slewing round of the apparatus on its base- 
board, the adjustment above spoken of is upset and the flame is 
induced to recover its tall equilibrium condition. The sounds 
now reach the flame in opposition of phase and _ practically 
neutralise one another. That this is sois proved in a moment. 
If the hand be introduced between either orifice and the flame, 
flaring ensues, the sound not intercepted being free to produce 
its proper effect. 
The analogy with Fresnel’s bands would be most complete if 
we kept the sources of sound at rest and caused the burner to 
move transversely so as to occupy in succession places of maxi- 
mum and minimum effect. It is more convenient with our 
apparatus and comes to the same thing, if we keep the burner 
fixed and move the sources transversely, sliding the base-board 
without rotation. In this way we may verify the formula, con- 
necting the width of a band with the wave-length and the other 
geometrical data of the experiment. 
The phase discrepancy necessary for interference may be in- 
troduced, without disturbing the equality of distances, by insert- 
ing in the path of one of the sounds a layer of gas having 
different acoustical properties from air. In the lecture carbonic 
acid was employed. This gas is about half as heavy again as 
air, so that the velocity of sound is less in the proportion of 
1:1'25. If / be the thickness of the layer, the 7e/ardation is 
25/3 and if this be equal to the half wave-length, the inter- 
position of the layer causes a transition from complete agreement 
to complete opposition of phase. 
films of collodion. The films most convenient for this purpose 
are those formed upon water by the evaporation of a few drops 
of a solution of celluloid in pear-oil. These cells were placed 
one in the path of each sound, and the distances of the cones 
adjusted to maximum flaring. 
into ove cell quieted the flame, which flared again when the 
second cell was charged so as to restore symmetry. Similar 
[May 8, 1902 
half wave-length of the sound. The experiment may be made 
in the lecture-room with the sensitive flame and one of the 
highest pipes of an organ, but it succeeds better and is more 
striking when carried out in the open air with a pipe of lower 
pitch, simply listened to with the unaided ear of the observer. 
Within doors reflections complicate all experiments of this 
kind. 
UNIVERSITY AND EDUCATIONAL 
INTELLIGENCE. 
Oxrorp.—The 235th meeting of the Junior Scientific Club 
was held on May 2 in the physiological lecture room at the 
Museum. Two papers were read, ‘‘ A New Type of Vertebrate 
Kidney,” by Mr. E.S. Goodrich, Merton College, and ‘* The 
Prussic Acid Problem,” by Mr. J. M. Wadmore, Trinity 
College. i 
The ninth Robert Boyle lecture of the Junior Scientific 
Club will be delivered by Prof. T. Clifford Allbutt, F.R.S., 
in Balliol College Hall on Tuesday next, May 13. - The subject 
will be ‘t‘ The Growth of the Experimental Method in Oxford.” 
THE honorary degree of LL.D. was conferred on Lord Kelvin 
on Monday by the University of Yale. 
A MEETING will be held at the Mansion House to-morrow, May9, 
at 3 p.m., with the Lord Mayor in the chair, in support of higher 
university education and research in London, with special refer- 
ence to the fund being raised for the endowment of University 
College and its incorporation in the University of London. All 
who are interested in national progress and the advancement of 
knowledge are invited to take part in this movement for making 
up in some degree the gaps in our educational system, and in the 
endeavour to place at the disposal of the inhabitants of London 
| facilities for mental training at any rate equal to those enjoyed 
Two cells of tin plate were | 
employed, fitted with tubes above and below, and closed with | 
by our continental neighbours. Among the speakers at the 
Mansion House meeting will be the Duke of Devonshire, Lord 
Brassey (chairman of the Appeal Committee), Lord Avebury, 
Mr. Ritchie, M.P., the Hon. Alban Gibbs, M.P., Sir Michael 
Foster, M.P., Principal Riicker, F.R.S., Mr. Lionel Phillips, 
and Mr. H. R. Beeton. 
Tue debate on the second reading of the Education Bill of 
the Government was opened in the House of Commons on 
Monday. Mr. Bryce gave reasons for believing that the Bill 
would not establish satisfactory local authorities, secure educa- 
tional improvement, or effect a final settlement of the education 
question, Referring to secondary education, Mr. Bryce said 
that the Bill promises to do nothing for it, though secondary 
education is the most urgent of all our educational wants. 
‘*Tt does not direct any inquiry or any scheme to be made 
for the reorganisation of secondary education. It does not 
impose any duty upon the new authorities to provide 
secondary education, however great the local need may be. It is 
The insertion of carbonic acid | 
effects were produced as the gas was allowed to run out at the | 
lower tubes, so as to be replaced by air entering above.! 
Many vibrating bodies give rise to sounds which are powerful 
in some directions but fail in others—a phenomenon that may 
be regarded as due to interference. The case of tuning forks 
(unmounted) is well known. In the lecture a small and thick 
wine-glass was vibrated, after the manner of a bell, with the aid 
of a violin bow. When any one of the four vibrating segments 
was presented to the flame, flaring ensued ; but the response 
failed when the glass was so held at the same distance that its 
axis pointed to the flame. In this position the effects of 
adjacent segments neutralise one another and the aggregate is 
zero. Another example, which, strangely enough, does not 
appear to have been noticed, is afforded by the familiar open 
organ pipe. The vibrations issuing from the two ends are in 
the same phase as they start, so that if the two ends are equally 
distant from the percipient, the effects conspire. If, however, 
the pipe be pointed towards the percipient, there is a great fall- 
ing off, inasmuch as the length of the pipe approximates to the 
1 Ina still atmosphere the hot gases zrisinz fiom lighted candles may 
be substituted for the layers of COs. 
NO. 1697, VOL. 66] 
purely permissive. It does not contain any suggestion for deal- 
ing with endowments or for the reorganisation of schools. It 
does not set apart the grant under the Act of 1890 as only ap- 
plicable to secondary education. It gives a rating power up to 
2d., with the possibility of increase by the consent of the Local 
Government Board. Secondary education ought to have had 
a Bill to itself, and it ought to have had a start of two or three 
years before primary education is thrown upon the same 
authority, if ever it is to be thrown uponit. Now, the probability 
is that secondary education will go to the wall.” Sir John Gorst 
urged in reply that the Bill creates an authority, or it gives to the 
authority already existing for technical education full powers 
for secondary education, and so may be said to do something 
for secondary education. As to the inadequacy of the funds 
available under the Bill, it was held that the County Councils 
had enough to begin with, ‘‘and,” added Sir John Gorst, ‘if 
this Bill is passed it will, at all events, make a beginning of 
secondary education, and when the authorities of counties and 
county boroughs see what sum of money is really required, I 
have no doubt the representations made by them to this House 
will be received with very fair consideration.” The debate was 
continued on Tuesday, and among the points discussed were the 
comparative merits of School Boards and County Councils as 
local authorities for education, need for better training of 
| teachers, the extension of the limit of a 2d. rate, and the need for 
generous grants from the Exchequer for secondary education. 
