August 13, 1908] 



NA TURE 



;53 



paring favourably with Pennsylvania bituminous coal, and 

 as anthracite is also met with, the investigation was 

 directed to determining the boundaries of the various coal- 

 fields and to ascertaniing the ages of the various coal 

 horizons. The occurrence of gold- and copper-bearmg 

 rocks is also recorded. 



The investigations of structural materials begun m 1905 

 has been continued, and a valuable report on Portland 

 cement, mortar, and their constituent materials has been 

 drawn up by Mr. R. L. Humphrey and Mr. \V. Jordan 

 (Bulletin No. 331). 



The work ot the survey includes investigations of under- 

 ground water, and in order to furnish trustworthy in- 

 formation on general principles, Mr. .M. L. Fuller has 

 drawn up a very instructive summary of the controlling 

 factors of artesian flows (Bulletin No. 319). The term 

 " artesian " is applied in the sense adopted by the survey, 

 namely, to designate the hydrostatic principle by which 

 conlined waters tend to rise in virtue of the pressure of 

 the overlying water-column, whether or not this pressure 

 is sufticient to lift the water to the surface and to produce 

 a flow. 



Lastly, there is the work of the mining division of the 

 survey.' The*outcome of the work, a volume of 1307 

 pages', contains the report on the mineral resources of the 

 United States for 1906. Much of the information given 

 has already been published as advance chapters. Suffice 

 it to say that the year 1906 was by far the most prosperous 

 ever known in the mining industry of the United States. 

 The total value of mineral products amounted to 

 380,000,000;., an increase of more than 15 per cent, over 

 the value of the output in 1905. Compared with the 

 previous volume of the series, noticed in Nature (vol. 

 Ixxvi., p. 257), several changes are apparent. The smaller 

 tvpe, which was tiring to read, has been abandoned, and 

 several new names appear as the authors of the various 

 chapters. This is in pursuance of the policy of the new 

 director of the survey of assigning all subjects to members 

 of the survey who are employed solely in the G-wernment 

 service. This has doubtless been conducive to economy, 

 but there is the loss of the authority given to the reports 

 bv the signatures of such experts of world-wide reputation 

 as Mr. James M. Swank, Mr. Charles ' Kirchhoff, Mr. 

 John Birkinbine, and Dr. George F. Kunz. The annual 

 reports of the last-named authority on precious stones were 

 works of originality and of great literary charm, whilst 

 the report on precious stones in the present volume is an 

 arid catalogue of facts. The reports on gold, silver, and 

 quicksilver are more successful, the technical knowledge 

 of the authors as mining geologists serving as compensa- 

 tion for their lack of experience in statistical work. 



The reports reviewed in this article cover 2239 pages. 

 It has, therefore, obviouslv been impossible in the space 

 rtvail.'ible to do more than indicate briefly the nature of 

 their contents in order to induce those interested in. the 

 various branches of economic geology dealt with to peruse 

 the original reports, which will well repay careful study. 



THE SYNCHRONISATION OF CLOCKS.' 

 HTHE hon. secretary of the British Science Guild has sent 

 us a copy of a report on the synchronisation of clocks 

 which has been adopted by the executive committee, and 

 is here reprinted. Steps are being taken to carry out the 

 recommendations contained in the report. 



The committee wish, in the first place, to direct 

 prominent attention to the fact that a very large amount 

 of most excellent work in the matter before the committee 

 has already been done by the General Post Ofiice in dis- 

 seminating standard time in London and large provincial 

 towns, and also to outlying districts in Great Britain, 

 though in the latter case the arrangements, perhaps, are 

 not quite so perfect as in the large towns. 



They also wish to state that private companies, lil^e the 

 Standard Time Company, Ltd., are doing excellent work 

 in the same direction in London and its neighbourhood. 

 Thev are, however, of opinion that much more has still to 

 be done before London and other parts of the country can 



1 Report of a Committee of the Rritish Science Guild on the subject of 

 the synchronisation of clocks in London, snd in other parts of Great Britain. 



NO. 2024, VOL. 78] 



be said to be in a satisfactory condition as regards the 

 time shown by its public clocks, and they consider the tiine 

 has come when public action is urgently demanded. 



Greenwich mean time is of course recognised as the 

 standard time for the whole of Great Britain, and this 

 time emanates from the inean solar clock at the Greenwich 

 Observatory. 



The problem, therefore, is solely how to make this time 

 available throughout the country in the widest and easiest 

 manner possible, and at the lowest possible cost to the 

 State or public, and also so as not to interfere in the 

 slightest degree with any telegraphic or telephonic services 

 at present m use. 



The present arrangements as to the dissemination of 

 this time in London and elsewhere may, perhaps, be 

 described with suflicient accuracy as follows : — 



Greenwich inean time signals are transmitted at the 

 sixtieth second of each sixtieth minute day and night to 

 the General Post Ofiice, London, and daily at ro a.rn. to 

 every telegraph office in the kingdom, when the signal 

 then sent from the mean solar clock at Greenwich Observa- 

 tory is received at the Central Telegraph Office in London 

 upon apparatus which is known as the chronopher,^ the 

 function of which is to distribute automatically the signal 

 to the larger provincial telegraph centres. 



By means of a clockwork arrangement, electrically con- 

 troll'ed by a regulator clock, the telegraph lines are discon- 

 nected from their respective telegraph instruments and are 

 joined to the relays of the chronopher at two minutes 

 before ten, in readiness for the signal from Greenwich. 

 The time current passes exactly at ten o'clock, and the 

 normal connections are restored by the clockwork at two 

 minutes past ten. 



From the large centres the word " ten " is signalled to 

 all the small towns and villages. 



In London " nine " is signalled to all London offices 

 connected to what is known as the " main inter-coinmuni- 

 cation switch " in the Central Telegraph Ofiice, and an 

 hour later, when the " chronopher " signals " ten " 

 o'clock time to provincial otTices, " ten " is also signalled 

 to the remainder of the London telegraph offices. 



From the Post Office the public may in London, by 

 arrangement and by paying a certain annual sum, obtain 

 the hourly Greenwich mean time signals. 



In other cases, one or other of two daily signals, at ten 

 o'clock and at one, can be sent to places in the provinces, 

 but the number of private subscribers for such signals is 

 relatively small. 



.'\t present the signals from Greenwich sent via the 

 Post Office onlv give the indications of the exact time by 

 sounding bells 'or deflecting needles, and are not generally 

 utilised to influence individual clocks or to control them, 

 it being left to the individuals in charge of such clocks 

 to make use of these signals, and to set their clocks 

 accordingly. , . . . u 



It is at this point that much is to be desired in the 

 present arrangements, for there is no doubt that many 

 clocks are not as accurately set as they should be. 



In addition, these time signals are communicated, 

 amongst others, to private companies like the one previously 

 referred to, and this company, or similar companies, make 

 it their business automatically to re-distribute them to 

 their subscribers in such a way that the electrical signals 

 actually set the clocks of the subscribers to the correct 

 standard time at the moment of each signal. 



It would appear, therefore, that there is no general system 

 by which the public is provided with the means of getting 

 exact standard time, such as would be the case if there 

 were an arrangement by which time balls in prominent 

 positions could be electri'callv dropped, or time guns fired 

 at any fixed hour. In the case of London, the area to be 

 covered would prohibit any such treatment of the case. 



The committee are strongly of opinion, and think it 

 highlv desirable and important, that arrangements should 

 be made so that a number of public clocks in different 

 districts of London and in other large towns, and perhaps 

 the clock at a telegraph office in smaller towns and 

 villages, should at certain hours be automatically corrected 

 to agree with the true standard or Greenwich mean time, 

 and that these clocks should be known as standard clocks, 

 and be thus marked or labelled. 



