December 12, 1912] 



NATURE 



421 



both rooms at a height of Si ft. from the floor, and 

 serves to support shafting and pulleys, which are set 

 in motion by an electric motor in the larger room. 

 Gas and water pipes also run along this beam, which 

 carries, in addition, wires from an electric clock, and 

 a tube supplying artificial respiration, so that these 

 are all available throughout the laboratory. A floor 

 channel running benea'th the beam carries off waste 

 water, and, in "addition to wall switches, a number 

 of floor plugs are inserted in its neighbourhood to 

 supply lia-ht and power where necessary. This labora- 

 tory is fitted up with the ordinary experimental ap- 

 paratus, and with a small centrifuge and incubator 

 for haemolysis work. 

 The second floor contains a small preparation and 



places in the body of the laboratory and stand round 

 and above the demonstration table. In this way it is 

 hoped to be able to correlate the lecture, the practical 

 work, and the demonstrations more closely than is 

 possible when these are all given in different courses 

 and in different rooms. 



y Coilege, London, 



drug room for use in the lectures and demonstrations 

 andlhe large lecture-room laboratory. This measures 

 48 ft. by 25 ft., and is fitted up with lecture desk, 

 blackboards, and projection lantern, and with practical 

 room benches for elementary work in pharmacology. 

 A recess off the lecture-room, i8 ft. by 13 ft., is 

 furnished with three tiers of standing places rising 

 one above another, from \vhich the spectators look 

 down directly on the experimental table below. The 

 students are' expected to perform the simpler experi- 

 ments in the laboratory, and these will be discussed 

 and elucidated from the lecture table. The more 

 complicated experiments will be done by the demon- 

 strator on the special table in the recess, and when 

 these are in progress the students will leave their 



NO. 2250, VOL. 90] 



MATHEMATICS AND PHYSICS AT THE 

 BRITISH ASSOCIATION. 



THE presidential address was delivered by Prof. 

 H. L. Callendar at 10 a.m. on Thursday, 

 September 5. This was published in full in Nature 

 of September 5 (p. 19). 



Wireless Telegraphy. 

 The principal discussion arranged 

 was a joint one with Section G on 

 the scientific theory and outstanding 

 problems of wireless telegraphy ; it 

 was opened by Prof. J. A. Fleming. 

 Dr. Fleming had drawn up a list of 

 twenty-four questions to which 

 definite answers are still required. 

 In the short time available to him it 

 was impossible to go seriatim 

 through these. After outlining the 

 general methods of signalling now- 

 employed, he pointed out that the 

 chief question was how such waves, 

 if they are true Hertzian waves, are 

 propagated a quarter of the way 

 round the earth. The mathematical 

 investigations of Prof. MacDonald, 

 Lord Rayleigh, the late Prof. H. 

 Poincare, and of Dr. Nicholson 

 seem to have proved that diffraction 

 alone will not account for the 

 phenomenon, even though the waves 

 as used by Marconi have a wave 

 length of nearly four miles. Prof. 

 Sommerfeld had come to the con- 

 clusion that there must be "surface 

 waves " at the boundary of the 

 earth and atmosphere, and that 

 these vary in amplitude inversely as 

 the square root of the distance, and 

 are sufficiently feebly damped in a 

 horizontal direction to be propagated 

 long distances, irrespective of irre- 

 gularities of surface. Another 

 theory has been based by Dr. Eccles 

 upon the ionisation of the atmo- 

 sphere. If the velocity increases 

 with the ionisation, the upper part 

 of a wave may travel faster than 

 that near the surface, and the direc- 

 tion of propagation will be deflected 

 downwards. 



Closely connected with this is the inhibiting effect of 

 daylight! Absorption due to ionisation is not sufficient. 

 Refraction owing to varying dielectric constant arising 

 from ionisation "may be operative here. Many other 

 problems require elucidation, such as the greatly 

 reduced signalling distance at dawn and dusk, the 

 inequality in north-south and east-west transmission, 

 the theory of directive antennae, and the location of 

 the direction of the arriving waves. 



In the discussion Dr. W. Eccles directed attention to 

 his paper read before the Royal Society in June last. 

 In order to account for the great difference between 

 day and night transmission it seems necessary to 

 suppose that there exists in the upper atmosphere a 

 permanently ionised layer that is not dependent on 



