47S 



NA TURE 



[June 17, 1909 



catcly moving sliders on a 6-fccl V-and-pl;inc bed, so that 

 the two dilininK lines arc adjusted between the spider- 

 lines of the micrometer eye-piece in each case ; (2) to 

 replace the standard by the copy to be tested, so that 

 the defining line near one end is similarly adjusted under 

 the corresponding microscope; then, if the other defining 

 ?nark is not also automatically adjusted under the second 

 microscope which carries the glass interference plate, as 

 it should be if it is an exact copy, (3) to traverse that 

 microscope until it is so adjusted, and (4) to observe and 

 count the number of interference bands which move past 

 the interference spot during the process. The difference 

 between tlie bars is this number multiplied by the half- 

 wave-le;iglh of the light in which the bands are produced. 

 The paper also gives an account of the electrical and 

 thermal arrangements, as well as of the foundation 

 masonry of the new comparator room. The temperature 

 of the whole room is controlled entirely electrically, being 

 maintained constant at the ofTicial temperature, 62° F. 

 The thermostatic arrangements are of an original 

 character, and of two different independent types — a 

 thermometric and a resistance type. — The use of wave- 

 length rulings as defining lines on standards of length : 

 Dr. A. E. H. Tutton, The delicacy of the method of 

 measurement in wave-lengths described in the preceding 

 communication calls for a corresponding refinement in the 

 engraved lines which form the defining lines of the length 

 of a standard yard or metre or other line-measure bar. 

 The defining lines on the imperial standard vard are 

 sharp-edged, but contain the equivalent of forty inter- 

 ference bands of red light in their thickness, and the 

 Benoit defining lines of the platinum-iridium copy made 

 in 1002 are not only very ragged-edged, but contain fifteen 

 interference bands in their thickness. The author has 

 been in communication with Mr. J. II. Gravson, of 

 Melbourne, whose fine rulings have recently evoked such 

 interest among microscopists, and after a long investiga- 

 tion has found that wonderfully satisfactory rulings on the 

 scale of 40,000 to the inch can be made on polished 

 speculum metal, covered with a thin cover-glass cemented 

 only at the corners away from the rulings. Now the 

 forty-thousandth of an inch is a single wave-length of 

 red light (for Ha=i '38710 inch and Cd red= 1/30450 inrhl, 

 .so that the interval between any adjacent pair of these 

 lines is equivalent to only two interference bands. The 

 thickness of each line, which is absohitelv sharo-edged, 

 is less than a single interference band. The author has 

 therefore devised a defining mark in these rulings, which 

 he terms a " Tutton location signal," to distinauish it 

 from the " Benoit defining line." It consists of five such 

 parallel lines spared one forty-thousandth of an inch apart, 

 with a pair of strong " finder " lines outside them and 

 parallel to them, and another pair of similar finder lines 

 perpendicularly transverse to them, to indicate a central 

 part of the lines for use. The central line of the five fine 

 Grayson rulings is the defining line. These location 

 signals can also be ruled on platinum-irid'um, and with 

 less success on gold and invar ; but the result on speculum 

 metal is so very superior that a large number of location 

 signals have been made on this metal by Mr. Gravson 

 for the Standards Department. The paper indicates the'r 

 possible mode of use, not only as the end-mark defining 

 lines of standard bars, but for a new mode of determining, 

 by a sfepning-off process of reneated doublings, the total 

 number of wave-lengths of red cadmium light contained 

 in the British yard. 



Linnean Society. June 3.— Dr. D. H. Scott, F.R.S.. presi- 

 dent, in the chair. — Calantitcs (Calamitina) Schulzci, 

 Slur, and on the correspondence between the length of 

 internodes and the position and function Of the short inter- 

 node in the genus Calamiles and in the recent Equisetacex : 

 A. R. Horwood. The author stated that a specimen of 

 rnlniiiilfs Schiilzei, Stur, shortly to be figured, exhibits 

 graphir.illy the fistular character of the stem in Oalamites, 

 .1 specimen 3 feet long having been split into two portions 

 Innglludinallv and so preserved. In the .same specimen 

 [from the Main Coal, Slanlon-imder-Bardon, I.eics.) and 

 in another from Briglinuse. Yorks. provisionally referred 

 to this species, the regularly uniform length and position 

 of a short internode at the rominencement of each period 

 NO. 2069 . VOL. Sol 



of uniformly longer internodes are specially marked. .As 

 a result of a study of this specimen and of a comparison 

 made between it and specimens of the recent species of 

 Kquiselum, it is found that there is a strong resemblance 

 between the two groups, Calamarica; and Equiselace.T;, 

 in the position of the short internode, and a marked 

 similarity in the uniform rate of increase or decrease in 

 the length of the internodes in both groups also, most 

 apparent in Calamitina, but probably in a modified form 

 in Eucalamites and Stylocalamites, and in subterranean 

 stems of 5. Suckoivii there is a strict homology. — The 

 Cephalochorda — " aniphioxides " — of the Scalark expedi- 

 tion : H. O. S. Gibson. — The .Mcyonaria of the Scalark 

 expedition: Prof. J. .\. Thomson. 



Mathematical Society. June 10. — Sir W. D. Niven, 

 presidinl. in ihi- chair. — The behaviour at the poles of a 

 scries of Legendre's functions representing a function with 

 infinite discontinuities : F. J. W. Whipple. — .An analogue 

 of Pascal's theorem in three dimensions: \V. II. Salmon. 

 — Some symbolic.il expressions for the climinant of two 

 binary quantics : .\. I.. Dixon. 



Edinburgh. 



Royal Society, May 17. — Dr. John Home, F.R.S., 

 vice-president, in the chair. — A simple radioscope and a 

 radiometer for showing and measuring radio-activity : Dr. 

 J. Aitk«n. The instruments were a natural development 

 of his own and C. T. K. Wilson's investigations on 

 cloudy condensations. A U-tube about 2 cm. internal 

 diameter was filled partly with air and partly with water. 

 The open end of the tube was in connection with a rubber 

 ball, by which pressure on the enclosed air could be in- 

 creased and diminished at will. The rubber ball was com- 

 pressed by a simple, suitable mechanism of hinged levers. 

 When the pressure was suddenly diminished by relief of 

 the ball after compression had been applied, fog cloud 

 might be observed in the air space. After a few alternate 

 compressions and reliefs of pressure the cloud ceased to 

 form, the air being purified of natural nuclei. When, how- 

 ever, a radio-active body was brought near, the relief of 

 pressure was accompanied by formation of cloud. Various 

 forms of the radioscope were described. To convert the 

 instrument into a r.adiometer. Dr. Aitkcn made use of his 

 method of counting the drops as they fell on a surface 

 ruled into small squares. The instrument was not capable 

 of the same accuracy as Wilson's form of apparatus, but 

 it was simple and easily worked, and could give results 

 of quantitative value in comparing the radio-activity of 

 different substances. — Mendelian action on differentiated 

 sex : Dr. D. Berry Hart. After referring to the well- 

 known facts that tiie male and female genital tracts con- 

 tain, not only the potent elements proper to the sex, but 

 also non-potent elements of the opposite sex. Dr. Hart 

 proceeded to apply the principles of Mendelism, regarding 

 the non-potent elements as recessive and the potent 

 elements as dominant in Mendel's sense. If the genital 

 tract contained dominant and recessive determinates, then, 

 in Weismann's terminology, the zygote from which they 

 arose contained dominant and recessive determinants, and 

 this made it an impure determinant. To get such a 

 hcterozygotc two varieties of gamete seemed to be neces- 

 sary, viz. a non-sex and sex male gamete and a non-sex 

 and sex female gamete. By the crossing of a sex male 

 gamete and a non-sex female gamete, and of a sex female 

 gamete and a non-sex male gamete, respectively, male and 

 female zygotes were produced — variation zygotes. Evidence 

 was given that the dominant and recessive genital deter- 

 minants were not segregated in the gametes, but com- 

 bined in the sex gamete. The origin of the gametes was 

 discussed in relation to the Owen-Weismann law of the 

 continuity of the gcrm-rclls. Ovarian and testicular 

 teratomata were regarded as derived from a non-sex 

 gamete, which, owing to imperfect reduction from a 

 primitive germ-cell, retained some power of zygotic develop- 

 ment. The general view was that dominance and re- 

 cession acted on differentiated sex, but that the dominant 

 and recessive genital determinants were in the sex gamete, 

 and were not segregated in the gametes as the theory of 

 gametic segregation demands. The dominant and re- 

 cessive dements arc not segregated in the human race, 

 but arc segregated in the free-martin, and probably in 



