July 26, 191 7] 



NATURE 



41 1 



fully dealt with by a special society (the Optical 

 Societ>'), and overlapping is most undesirable in 

 matters of publication. 



The original papers attain a very creditable standard 

 for so young a society- and so new a subject. Prof. 

 Boswell's work on British glass sands is already widely 

 known and appreciated, since it has already been more 

 or less completely published elsewhere. Mr. C. J. 

 Peddle describes trials of British sands as substitutes 

 for some of foreign origin, and his results are ex- 

 tremely hopeful, provided that careful treatment in 

 regard to grading and washing is applied to the 

 British materials. Mr. F. T\\yman deals with the 

 annealing of glass, and describes a method of testing 

 the glass for strain and for its disappearance by means 

 of a special form of polarimeter; the modification 

 ascribed to Mr. F. E. Lamplough, however, is not 

 novel, as the writer saw it in use more than 

 fourteen years ago. Nor does Mr. Twyman make it 

 quite clear that his reasoning is not applicable to any 

 but thin glass vessels, such as the beakers he refers to. 

 In such thin glassware all that is required is uniform 

 cooling from the " annealing temperature " of Mr. 

 Twyman ; in thicker p-lass, however, such uniformity 

 as betA\'een exterior and interior portions can be ob- 

 tained only by verv slow cooling. 



.\part from detailed criticism of particular points, the 

 whole volume clearly shows the vitality of the new 

 society and the need for the co-ordinated study of glass 

 and glass manufacture from the scientific point of 

 view. It is to be hoped that all branches of the 

 British glass industr\-, which has received a rejuvenat- 

 ing impulse from the war, will support the new 

 society and thus facilitate the co-operation of science 

 in an industry that should be essentially scientific. 



PLANKTON RESEARCH AT PLYMOUTH. 



'X'HE May number of the Journal of the Marine 

 -*• Biological Association is devoted to an interesting 

 account of the investigations of the plankton of the sea 

 outside Plymouth Breakwater, made during the year 

 September, 1915, to September, 1916. The main sys- 

 tematic research has been conducted by Miss Lebour, 

 while Dr. Allen describes post4ar\al stages of fishes, 

 and Mr. Matthews gives an account of the variation 

 in the quantit\' of phosphoric acid present in the sea- 

 water. Miss Lebour used Lohmann's method of cen- 

 trifuging small volumes of sea-water (50 c.c), and 

 then actually counting the organisms so obtained. 

 Her results are in general agreement with those of 

 Lohmann (at Kiel) and Herdman and Scott (at Port 

 Erin). There are well-marked seasons of abundance 

 of microplanktonic organisms, diatoms occurring in 

 greatest quantity some time in the spring or early 

 summer, and then again in the autumn, while Peri- 

 diniales attain their maximum of seasonal abundance a 

 little later than the diatoms. The Peridiniales have 

 been very thoroughly investigated, and Miss Lebour 

 describes eight species which are new to science and 

 twenty-one species which have not hitherto been re- 

 [ corded from British seas. She also gives some records 

 of the occurrence of larval Trematodes, free-swimming 

 in the sea, and descriptions of the Helminth parasites of 

 Sagitta. These worms have been noticed many times, 

 and some of them are very familiar to planktologists, 

 I but no sound identifications have been made prior to 

 I the research now under notice. Sagitta is a host for 

 ! larval forms of Derogenes varicus and Pharyngora 

 I hacillaris, both well-known fish Trematodes. A larval 

 Ascaris al§p occurs, and two larval Cestodes, the species 

 of which are not identifiable. 



Mr. Matthews gives detailed accounts of his methods 

 1 of determining the exceedingly small quantities of 

 XO. 2491, VOL. 99] 



phosphoric acid which occur in sea-water, at the most 

 about 0-06 mg. of PjOj per litre. There is a well- 

 marked maximum at nearly the end of the year (in the 

 darkest days). The variations are dependent upon the 

 metabolism of marine plants, and the minimum quan- 

 tity of phosphoric acid occurs in April and May — that 

 is, at about the time when holophytic plants are taking- 

 most food substance from the sea-water. The larger 

 algae seem to be the principal factors for the curve of 

 variation in quantity of phosphoric acid not being the 

 reverse of that for variaticwi in abundance of diatoms, 

 as v.as at first expected. J. J. 



CORRECTION FOR ATMOSPHERIC RE- 

 FRACTION IN GEODETIC OPERATIONS.^ 



n^HE memoir before us is concerned with 

 -■• the correction for refraction in geodetic 

 operations between distant stations, especially 

 those differing considerably in altitude. The 

 author quotes Helmert's elaborate formula, 

 which gives the correction as a function of gravity, 

 atmospheric pressure, coefficient of expansion of air, 

 tension of aqueous vapour, temperature, and vertical 

 temp>erature gradient. The values deduced from the 

 formula are compared with those obtained by obser\'a- 

 tion over several bases in Italy and the Alps. The 

 results are grouped both by months and by hours of 

 the day; they show in a clear manner that there are 

 both diurnal and annual variations in the refraction 

 coefficient, which appear to be mainly due to the 

 changes in the vertical temperature gradient. The 

 following table shows the results of two series, the 

 coefficients in the first column being deduced from 

 the formula, and in the second by experiment. The 

 third column gives the observed vertical temperature 

 gradient. 



Coefficient of refraction at Diminution of 



noon temperature for 



Months * X 100 m. altitude 



From From in degrees 



formula experiment Centigrade 



Jan., Dec. ... 0-175 — 0-44 



Feb., Nov. ... 0-170 oi8r 0-55 



Mar., Oct. .. 0-158 0168 o-68 



Apr., Sept. ... 0-154 0"i59 074 



May, Aug. ... 0-145 0-154 0-79 



June, July ... 0-144 0-153 0-79 



The results of several measures of altitudes over 

 long bases in Italy (length 23 km., difference of alti- 

 tude 900 m.) show a range of somewhat over a metre, 

 and indicate that better results are obtained by using 

 the meteorological data of the lower station only than 

 by combining those of both stations. The memoir 

 closes with a table arranged to facilitate the applica- 

 tion of the correction for temperature to measured alti- 

 tudes in sur\-eying. A. C. D. Crommflin. 



THE COMPLEXITY OF THE CHEMICAL 



ELEMENTS.' 



II. 



The Periodic Law arid Radio-active Change. 



THE second line of advance interprets the periodic 

 law. It began in 1911 with the observ^ation that the 

 product of an a-ray change always occupied a place in 

 the periodic table two places removed from the parent 

 in the direction of diminishing mass, and that in 

 subsequent changes where a rays are not expelled, the 

 product frequently reverts in chemical character to 



1 " Sulla Determinazione del Coeffidente di Rifrazione Terrestre in Rase ad 

 Elementi Meteorologici." By Vincenzo Reina. (Roma : R. Accademia dei 

 Lincei. ser. v., vol. xii., Fasc. ii , 1916.) 



2 Discourse delivered at the Royal Institution on Friday, May 18, ky 

 Prof. Frederick Soddy, F.R.S. Continued from p. 418. 



