October 21, 1920] 



NATURE 



253 



Alexander McAdie. Consecutive observations have 

 now been published for thirty-four years. Atmospheric 

 pressure, air temperature, vapour pressure, relative 

 humidity, cloudiness, wind direction and velocity, and 

 precipitation are given twice daily, at 8 a.m. and 

 8 p.m., throughout the twelve months, and the means 

 and totals are entered for each month with the 

 differences from the normals for the thirty-four 

 years, 1886 to 1919. Wind frequency is given for each 

 month and for the year for each 45° of the compass, 

 and the mean and highest wind velocity. The dura- 

 tion of sunshine and the percentage of the possible 

 amount are also included. Phenomena showing the 

 advance of the season for each of the thirty-four 

 years are given, such as thawing of ponds, last snow- 

 fall and last frost in spring, first blossom and first 

 ripe fruit, first snowfall in autumn, and ponds frozen. 

 There are numerous constants and averages for the 

 thirty-four years, such as days with snow, hail, 

 thunderstorms, and fog. Rainfall and snowfall and 

 mean temperatures for each month of the thirty-four 

 years are entered in tables. In the introduction a 

 slip has been made in transposing the references to 

 tables ix. to xi. .\ detailed description is given by 

 Prof. Mc.\die of "a quick method of measuring cloud 

 heights and velocities," which will doubtless be useful 

 at aerographic stations. 



Batavia Observatory has issued a volume of 

 140 pages, giving in detail the meteorological and 

 magnetical observations for 1915, and also the 

 meteorological results for the several months for the 

 fifty years 1866 to tg^s and the means for the whole 

 period. The work is published by the Government 

 of East India, under the supervision of Dr. W. van 

 Bemmelen, the director. For half a century hourly 

 observations of many of the elements have been un. 

 interrupted. .A change has been made in the position 

 of the barometer during' 19 15 which reduces the daily 

 range of temperature of the attached thermometer 

 from 5° C. to only a few tenths of a degree — an 

 important factor when searching for the diurnal range 

 of atmospheric pressure. For wind velocity the 

 factor 3 has been used as formerly for the reduc- 

 tions, but it is found that the true factor decreases 

 with the increasing velocities of wind. The results 

 for fifty years probably give in many cases means 

 which will vary little by any increase in the length 

 of the period, but the fifty years may contain cycles 

 the means for which may differ considerably among 

 themselves. Rainfall results are given for fifty-two 

 years, and breaking these into two periods of twenty. 

 six years, the monthly averages are very different. 

 Roughly speaking, the rainfall for the latter twenty- 

 six years, 1890-1915, has increased in the .southern 

 winter months and decreased in the southern summer 

 months. Magnetical observations are given only for 

 1915; there are curves showing the monthly devia- 

 tions of the magnetic components from the mean 

 yearly values. 



The Report of the Committee on the Standardisa- 

 tion of the Elements of Optical Instruments just 

 issued by the Research Department contains much 

 information of prime importance to instrument- 

 makers. It fixes standard focal lengths and diameters 

 NO. 2660, VOL. 106] 



for telescope objectives, angles of prisms for binocu- 

 lars, and diameters of tubing and of screws and 

 pitches of the latter. It strongly advocates inter- 

 changeability amongst the products of the different 

 manufacturers, and points out that two years ago 

 the screws nominally of the same size turned out by 

 one optical firm only in the country were interchange- 

 able amongst each other. That firm has in a most 

 public-spirited way offered to supply the chasers and 

 gauges necessary to secure interchangeability. The 

 adoption by the Committee of the inch as the unit of 

 length will not permit of the principle of interchange- 

 ability being extended to instruments of Continental 

 manufacture. 



In the September issue of the Journal of the Franklin 

 Institute Dr. F. E. Pernot has written an interesting 

 and important paper on submarine-cable signalling. 

 Dr. Pernot gives the results of experiments carried 

 out by the members of the Signal Corps Research 

 Laboratory of the U.S. Bureau of Standards. Several 

 successful attempts were made to increase the carry- 

 ing capacity of a submarine cable by superposing an 

 alternating current on the existing system of direct- 

 current signals. It is pointed out that currents of 

 several frequencies can be used simultaneously, as 

 each message can be separated ty a suitable tuning 

 device. The author is to be congratulated on having- 

 determined the physical constants of a submarine 

 cable at various frequencies, both by calculation and 

 by experiment. It is shown that the design of suit- 

 able apparatus becomes a straightforward problem. 

 .Actual trials of these methods with cables as long as 

 700 km. were made, the results being in all cases 

 completely satisfactory. With longer cables difficulties 

 were experienced, but the experiments indicated that 

 it was possible to superpose at least one alternating 

 current on the existing duplex system of an .Atlantic 

 cable. From the theoretical point of view it is 

 interesting to note that the high-frequency resistance 

 of a submarine cable is greater than that computed 

 by Kelvin's formula. The effects of the steel armour- 

 ing and the uncertainty in the position of the return 

 currents would probably account for this. It was 

 found that 5 microvolts at the receiving end gave 

 good signals with the powerful amplifiers which are 

 now available. 



"The Gases Dissolved in Water" formed the sub- 

 ject of the Streatfeild memorial lecture delivered 

 by Mr. J. H. Coste at the Finsbury Technical College 

 on October 14. In a brief historical sketch reference 

 was made to the work of Henry, Dalton, and Bunsen 

 on the estimation of gases dissolved in water, and to 

 that of Dittniar in connection with the Challenger 

 Expedition. Curves were shown to illustrate the results 

 of Adeney's work on the rate of aeration of air-free 

 water, and reference was made to the investigations 

 of Torn0o, Winkler, Roscoe, and Dittmar on the 

 variation with tenip«'rature of the volumes of gases 

 dissolved in water, results being given for distilled 

 water and sea-water. The absorption coefficients 

 determined by Bohr and Bock were given, and a curve 

 depicting the manner in which solubility of oxygen 

 in water falls with rise of temperature was shown. A 

 method of collecting samples from .nnv depth was 



