Dec. 7, 1876J 



NATURE 



119 



they were represented by the composite Botryllidae, which 

 could be had in immense numbers in some of the shallower 

 parts at the entrance of the Zuyder Zee, mostly attached to 

 blades of the Zostera. The stones employed in the con- 

 struction of the great dyke, which are partly lyinj; loose, 

 were of importance, as they usually covered over the 

 haunts of numerous Crustaceans, Nemerteans, &c. A no 

 hss rich harvest was got from the driftwood now and then 

 met with, and from the wooden palings serving in the 

 construction of the wharfs, &c., in the harbour, which 

 were submerged at high tide. 



Altogether this first summer of the Dutch Zoological 

 Station gave ample proof of its practicability. It would 

 perhaps be a good idea to act conjointly in future with 

 the German men of science, and to add a third perma- 

 nent station to those proposed in the German Committee's 

 Report (Kiel and Heligoland), say at Flushing. If, then, 

 one other station were to be erected on the English or 

 Scotch coast (St, Andrew's Bay ?), a conjoint attack 

 could be made on the mysteries still hidden in that part 

 of the ocean which is inclosed by our neighbouring 

 coasts. The healthy competition which would arise out 

 of this division of the work to be done, can only be 

 favourable to the common end — an accurate knowledge 

 of the natural history of our own seas, and a constant 

 opportunity of studying their animal and vegetable pro- 

 ductions in the fresh state. 



SENSITIVE FLAME APPARATUS FOR ORDI- 

 NARY GAS PRESSURE, AND SOME OBSER- 

 VATIONS THEREON 



A GLASS or metallic tube, about 5 inches long, and 

 I in diameter, is closed at one end with a perforated 

 cork, through this cork slides a piece of ^ inch tubing, 

 about 6 inches long. One end of this is either drawn 

 out to a jet, or closed in the blow-pipe 



Aflame to reduce its diameter to about -j^^ 

 inch, and the other end is connected to a 

 gas supply. (Fig. i.) 



The outer tube is held in a suitable 

 support, and the inner tube is pushed 

 through the cork till it nearly reaches the 

 mouth of the outer one, and a light then 

 applied. It now gives a long steady 

 flame. 



Experiment I. — Lower the inner tube 

 till the flame is on the point of roaring. 

 It will now be found very sensitive to noise. 

 Snapping the fingers at a distance of eight 

 or ten yards will cause it to "contract 

 fully \ of its height. The most suitable 

 flame for this is about 6 inches high. 



Experiment II. — Adjust the gas to 

 give a flame of about 4^- inches high, 

 and gradually raise the inner tube. A 

 point will be reached at which the flame 

 becomes sensitive, not to noise, but note ; 

 and it will be found to respond to a cer- 

 tain note by dividing into two portions, 

 and while this note is produced it will 

 continue divided. It is difficult to keep I 

 the exact note by whisthng with the 

 mouth, and therefore a glass whistle with I 

 paper slider should be used, or, better ' 

 stilJ, a singing tube with adjustment. j 



Experiment ///.—Arrange two singing ; 

 tubes to give the responding note. The \ 

 flame divides. Now make one tube a 

 little sharper than the other, so as to beat 

 slowly. The alae of the flame alternately 

 recede and coalesce. 



! 



as to produce higher octaves of the responding note. 

 The flame will be unaffec'ed, as though in perfect 

 silence. 



The dimensions of the instrument are open to great 

 variation, and also the size of the flame. For lecture 

 work, a flame \\ or 2 feet would be more suitable, though 

 less sensitive, and neither dividing nor shortening so per- 

 fectly as the sizes given above. It will act effectively 

 with any pressure of gas, from -^ inch (of water) up- 

 wards, and the sliding jet makes it equally sensitive with 

 a large or small gas supply. 



Observatitns on the Escape of Gas from Contracted 

 Openings, and on a Differential Pressure Indi- 

 cator. 



Glass tubes of about | in. bore are joined as shown in 

 Fig. 2. At D the tube is slightly bent so as to retain a 

 little drop of water. The gas enters at c, and then divides 

 into two channels, one towards B, the other towards A. 



i ! 



D 



n 



Fig. I. 



Experiment IV. — Using the whistle ; blow it so hard 



r 



Fig. 2. 



If one of the exits be contracted, say B, then the water 

 moves towards A. Certain precautions have to be ob- 

 served, the conditional arrangements of which need not 

 be mentioned here. 



Experiment I. — Connect to each, A and 1, a tapering 

 jet, and C with the gas supply. Get the water stationary. 

 Now light, say, B, the water will move towards A, 

 showing that the exit of the gas is retarded by being 

 ignited. 



This is rather a remarkable result, seeing that the gas 

 is hotter, and therefore more mobile, and also that the 

 heat must enlarge the aperture. Now light A, and the 

 water will return to zero. 



Experiment II. — Connect B with a sensitive flame 

 apparatus, A remaining as before, light and adjust to 

 zero. Now sound the responding note and the water 

 moves towards A, showing that the outflow of gas is 

 retarded by a certain note. Now adjust the sensi- 

 tive flame for noise, and rapidly snap the fingers 

 or stamp the foot, and the water will still move to- 

 wards A. 



Experiment III. — Arrange as in II., then extinguish 

 the sensitive flame and readjust to zero. Produce the re- 

 sponding note, and the same movement of the water will 

 be observed. This shows that an issuing jet is affected 

 in the same manner by a sound, whether ignited or other- 

 wise. 



Experiment IV. — Fix the sensitive flame apparatus 

 adjusted for note under a large jar open at both ends. A 

 large stoppered gas jar answers very well. Fix three balls 

 of spongy platinum, a, b, and c, upon a piece of thin 

 platinum wire so that the point of the quiescent flame 

 just reaches b, and the points of the responding flame reach 

 a and c respectively. Now extinguish the flame with- 

 out turning oflf the gas. The issuing gas will cause the 

 ignition of b. Now sound the responding note, and b will 

 cool, and a and c will be ignited. This confirms the 

 previous observations, and forms a rather pretty lecture 

 experiment. The object of the gas jar is merely to 

 protect from air currents. 



R. H. RiDOUT 



