August 14, 1913] 



NATURE 



61 



advance since the invention of the chronometer 

 has been the application of wireless telegraph}-, 

 of which the possibilities began to be considered 

 in this connection very soon after Marconi's first 

 success. 



Few unexplored districts of the habitable globe 

 would be beyond the reach of a powerful wireless 

 installation if distributing stations were an 

 ordinary adjunct of every national observatory, 

 and it is likely that the network of stations will 

 be able to distribute Greenwich time over the whole 

 of the oceans. 



For general purposes time-determination within 

 a quarter of a second is sufficiently exact, but this 

 accuracy at a fixed observatory was by no means 

 always attainable under old conditions, since a 

 week of cloudy skies, especially if accompanied 

 by considerable changes of temperature, would 

 leave the fixed observatory almost as dependent 

 on the rate of a chronometer as a ship at sea. 

 Here, however, the new development steps in 

 and suggests that, since it is not likely to be 

 cloudy everywhere, the time can be checked by 

 that of an observatory perhaps thousands of miles 

 away ; so that no error approaching a second of 

 time need be feared. 



This state of things, needless to say, is not yet 

 universal ; but there is no doubt about the begin- 

 ning that has been made. The distributing- 

 stations, requiring great electrical power and 

 much more costly and elaborate fittings, 

 will always be comparatively few, but the receiving 

 stations can also take part in the scheme. The 

 Eiffel Tower station sends out the Paris Observa- 

 tory determination of Greenwich mean midnight, 

 for instance, and this is received, say, at Green- 

 wich with a modest equipment and compared with 

 the Greenwich determination. The difference can 

 be sent without much delay to Paris by post or 

 telegram. When it is remembered that at night, 

 under favourable conditions, signals from the 

 Eiffel Tower have been received at a distance well 

 above 3000 miles (5200 kilometres), it will at once 

 be seen how this device will prevent any accumula- 

 tion of error due to a spell of bad weather. 



But a quarter of a second cannot be regarded 

 as indicating the possible limit of accuracy attain- 

 able. By employing clocks with a small difference 

 of rate, coincidences of beat can be noted with 

 great accuracy, the arrangement forming whal 

 might be called an acoustic vernier. For example, 

 if two sidereal clocks supposed to be synchron- 

 ised differ by a small fraction of a second owing 

 to a difference of lag in taking up the current 

 from the control clock, this difference can be 

 readily obtained by comparing' each with the same 

 mean solar clock, as the coincidences will occur .' 

 a definite interval. An accuracy of one-hundredth 

 of a second (to use a loose, convenient phrase) is 

 not by any means impossible in this way, and 

 Commandant Ferrie suggests one-thousandth of a 

 second as practicable. In this way may be 

 measured not only the lag between the clock beat 

 and the closing of the transmitting- circuit, the 

 additional lasr before the Hertzian waves actually 

 NO. 2285, VOL. 91] 



leave the Eiffel Tower, and the lag at the receiving- 

 station, but also the velocity of the waves them- 

 selves, which can be measured, he says, with an 

 error of less than 3 percent., though this velocity 

 nearly reaches 200,000 miles per second. 



It is part of the routine of the station to trans- 

 mit time-signals by night and by day, the latter 

 being followed by a meteorological report giving 

 barometric pressure, direction and force of the 

 wind, and the state of the sea for six stations 

 in and around the Atlantic. Similar work, at 

 times arranged not to interfere with that of the 

 Eiffel Tower, is done at the German station at 

 Norddeich, and other extensions will doubtless 

 follow. Japan, at any rate, has already started 

 an independent system. 



Commandant Feme's account gives very full 

 mechanical details of each step of the process, 

 and should be of great interest to the growing 

 number of people possessing private wireless 

 installations, some of whom compare their time 

 almost daily with both Eiffel Tower and Nord- 

 deich. There is no indication at present of any 

 intention to erect a distributing station at Green- 

 wich, and, as stated above, it may be considered 

 unnecessary, the fortuitous presence of the Eiffel 

 Tower giving Paris a great advantage, as its 

 range goes far bevond the British Isles. 



W. W. B. 



NOTES. 



The exhibition of specimens illustrating the modifi- 

 cation of the structure of animals in relation to flight 

 which has been in preparation for many months at 

 the Natural History Museum will be open to the 

 public on Friday, August 15. It occupies the fourth 

 bay on the right of the central hall, and comprises 166 

 mounted objects and twelve microscopic specimens for 

 the purpose of elucidating- the subject in a popular 

 manner. The adaptation of each kind of flying animal 

 for aerial locomotion is explained, and the changes 

 that must have taken place in the structure of the body 

 before the animal could really fly are indicated, and 

 attention is directed to the remarkable fact that the 

 power of flight has been evolved independently in 

 different groups of animals — e.g. bats, birds, Ptero- 

 dactyles, and insects. 



The death is announced, in his fifty-first year, of 

 Prof. Edwin Goldmann, honorary professor of surgery 

 in the University of Freiburg i/B. since 1892. Prof. 

 Goldmann 's scientific career and work are referred to 

 in an appreciative notice contributed by Prof. 

 Ehrlich to The Times of August 13, and here 

 summarised : — As a pupil and friend of the 

 famous pathologist Weigert, he mastered the 

 technique of microscopy completely. In early days he 

 busied himself principally with researches into bio- 

 chemistry. Here he turned his attention especially 

 to the study of minute vascular changes. And then 

 an inner impulse compelled him to devote himself to 

 the important field of cancer research, and by in- 

 genious experiments to advance our knowledge of this 

 difficult problem. His great work with a large 



