fc: 



April 22, 1922] 



NA TURE 



523 



t up into groups which are rendered audible to the 

 wireless operator by means of a telephone receiver, 

 which gives a click for every wave train, the signal 

 being, of course, first rectified by the valve, so that a 

 succession of musical sounds are heard in the telephone 

 receiver corresponding to the Morse alphabet. The 

 intermediate or high frequencies in each wave train 

 are beyond human audibility, and are therefore not 

 heard. The wave generated by the valve is, however, 

 a continuous one, that is to say, every time the sending 

 key is pressed a group of continuous waves are sent 

 out at a frequency determined by the wave-length.' 

 To render them audible in the telephone at the re- 

 ceiving end, a local valve oscillator is used for generating 

 frequencies slightly lower or higher than the received 

 signal and, by heterodyning or superimposing one on 

 the other, a frequency equal to the difference of the 

 two notes is heard in the telephone receiver. This 

 allows of exceedingly fine tuning, fo.- the frequency 



Probably, the most interesting application of the 

 thermionic valve is its use in radio-telephony. Here 

 the valve is used to generate continuous waves in a 

 suitable circuit and, by means of a microphone, the 

 voice of the speaker is made to vary the amplitude 

 of this wave at the different audible frequencies which 

 are used in speech formation. These modulations 

 are then conveyed to the aerial, and the telephone 

 diaphragms at the receiving end are correspondingly 

 stimulated and reproduce the speech exactly as trans- 

 mitted. Numerous other uses have been found for 

 the thermionic valve, among which may be mentioned 

 direction finding, the navigation of aeroplanes in 

 flight, its use as a rectifier for charging batteries. 

 Communication between moving trains, and the control 

 of energy at great distances. In the latter direction 

 mention may be made of communication by radio- 

 telephony having been definitely established between 

 England and Australia. Wherever a succession of 



of the local generator being under the control of the , signals can be received, they can always be amplified 



receiving operator, the difference in pitch is adjusted 

 to 1000 cycles, the best value for human reception. It 

 will therefore be seen that frequencies of as low as 

 I can readily be detected, although, when the difference 

 becomes very small, there is a tendency for one oscillator 

 to pull the other into step. 



and made to operate selective electrical or mechanical 

 relays for controlling power of any magnitude. The 

 future holds a wonderful vision of vast operations at 

 one end of the earth, being controlled by mankind 

 at the other without any other medium than the 

 aether. 



Obituary. 



Prof. Philippe A. Guye. 



BY the death of Prof. Philippe Auguste Guye, on 

 March 27, Switzerland loses one of the most 

 eminent of her savants, and the world of science 

 is th6 poorer by the passing away, in the full matur- 

 ity of his intellectual powers, of an assiduous and 

 successful cultivator of natural philosophy, distin- 

 guished alike for the range and profundity of his know- 

 ledge, the force of his genius, his originality, his 

 ingenuity and remarkable experimental skill. Geneva 

 has long been a home of science ; some of her citizens 

 are among the most honoured of its votaries, and Guye 

 now assumes his due position on a roll already made 

 illustrious by the names of Saussure, De La Rive, and 

 Marignac. 



Philippe A. Guye was born at Saint-Christophe 

 (Vaud) on June 12, 1862. His earliest scientific studies 

 were made at the University of Geneva, where he worked 

 under Graebe, with whom he published papers on 

 diphthalyl and on naphthalene hydrides — a modest 

 enough theme for the 'prentice hand — mainly a repeti- 

 tion of Graebe's observations of ten years previously, 

 which seemed to have been called in question by the 

 subsequent work of Agrestini. After taking his doctor- 

 ate he repaired to Paris, where he remained some years, 

 working in the laboratory of Friedel. Here he appears 

 to have come under the influence of ideas on spatial 

 chemistry which science owes to Le Bel, and much of his 

 work during the next few years was devoted to their 

 development. In 1892 he was recalled to Geneva to 

 occupy the chair of theoretical and applied chemistry in 

 the university of that city, to which he remained 

 attached for thirty years. During this period Guye, by 



NO. 2738, VOL. 109} 



his energy and personal influence, his organising power, 

 and the catholicity of his scientific aims, made an 

 indelible impression on the academic life and activities 

 of the university. He surrounded himself with a body 

 of earnest and enthusiastic workers, attracted from all 

 parts of the world, to whom he gave freely from a 

 wealth of ideas which ranged over every department of 

 chemical and physical science. It is estimated that 

 upwards of 600 communications emanated from the 

 Geneva laboratory while under his direction, some 200 

 of which bore his own name alone, many others 

 being joint contributions by himself and his pupils. 

 His own work was characterised by a rigorous sense of 

 accuracy, by caution and a recognition of possible 

 sources of error, amounting almost to intuition, com- 

 bined with a capacity for generalisation and a flair 

 for fruitful hypothesis which seemed, at times, like 

 divination. 



Although Guye began his scientific life under the 

 guidance of Graebe, and at a time when the theory 

 of organic chemistry and its technical applications 

 were developing with extraordinary rapidity and 

 success, systematic organic chemistry of the type with 

 which the name of his eminent teacher is asso- 

 ciated had few attractions for him, and it is doubtful 

 whether Graebe's teaching and example had any per- 

 manent influence on his career. At all events, on his 

 election to the Geneva chair he embarked upon the long 

 series of investigations on problems of physical chem- 

 istry on which his fame mainly rests. He was early 

 attracted to the many issues to which the molecular 

 theory of Van der Waals gave rise. He discovered a 

 series of new relations between the physical constants 

 of liquids and their molecular magnitudes, and he greatly 



