April 24, 1902J 



NA TURE 



601 



we substituted 

 and 



= 35349 -«W2; N„= 109675 



;u= ]i -19126 + 0'00iO3W + (0-04377 + I3W=X iQ-') (I -3'"'")!) 

 where 



« = io'a~' ; a = o-2233 ; W= atomic mass, and m= i, 2, 3. . . 

 This formula gives the second principal series of the three 

 metals ; the first principal series are obtained by increasing the 

 value of jn by iS2W^ x io~'. The agreement between the 

 observed and calculated numbers is very close. The formula, 

 though empirical, involves only seven adjustable constants, and 

 it represents in the table, given in the paper, thirty-two lines. 

 It thus affords striking evidence for the fundamental identity of 

 type of the spectra of the three metals to which it applies, and 

 indicates that their difterences depend on the atomic mass alone. 

 This evidence is further strengthened when it is remembered 

 that, being only an approximation to an unknown formula, it 

 will naturally come nearer it for large values of m than for small 

 ones. Additional evidence supporting 

 these views is given by the above obser- 

 vations upon the subordinate series of 

 these three metals. The fundamental g^ 



lines in the spectra of calcium, strontium 

 and barium are given by the formula 



« = 24i7o-o-3232W-. 



Many points of interest are revealed 

 by a study of these diagrams, but per- 

 haps the greatest interest lies in the com- 

 prehensive view one gets of the order of 

 change in the properties of the elements. 

 The diagram of densities is easier to 

 understand than that of melting points, 

 and the double connections in it, from 

 sodium to potassium and copper, from 

 magnesium to calcium and zinc aod from 

 aluminium to scandium and gallium, are 

 seen to be quite natural. The changes 

 in some of the corresponding lines in 

 the spectra agree with the changes in 

 the densities and melting points of the 

 elements. Other lines in the same spectra 

 change in a manner which is independent 

 of these. 



The whole study indicates that the 

 properties of the elements are funda- 

 mentally due to the structure of the atoms 

 as revealed by their spectra rather than 

 to the quantity of matter in them. It 

 seems, for instance, inconceivable that 

 the transition from calcium to strontium 

 proceeded through the intermediate 

 elements when we consider that the 

 strontium atoms must have a similar 

 structure to those of calcium, and that 

 this structure is so simple that the funda- 

 mental spectrum of each of these elements 

 consists of a single line. The anomaly, 

 according to MendeleefTs law, in the 

 atomic masses of tellurium and iodine 

 is further evidence of this. The genesis 



was not in the direction of tellurium to iodine, but from, or 

 perhaps through, oxygen and fluorine respectively. 



February 6. — On the increase of electrical resistivity caused 

 by alloying iron with various elements to the specific heat of 

 those elements. By Prof. W. F. Barrett, F.R.S. 



In this paper the author draws attention to a connection which 

 appears to exist between the electric conductivity of certain alloys 

 of iron and the specific heats, and hence atomic masses, of the 

 particular elements with which the iron is alloyed. In previous 

 memoirs, the author, in conjunction with Mr. W. Brown, has 

 determined the electric conductivity and magnetic permeability of 

 1 10 diflerent alloys of iron prepared with great care by Mr. R. A. 

 Hadfield, of Sheffield.' The results of these experiments show 

 (l) that the conductivity of iron is diminished by alloying it 



with another metal even though that metal be a much better 

 conductor than iron ; {2) that this reduction of conductivity is 

 not related to the resistivity of the added metal ; on the 

 contrary, an alloy of very high specific resistance can be 

 produced by adding to iron an element of much lower specific 

 resistance than the iron itself, e.g. the metal aluminium 

 is upwards of three times better a conductor than iron, yet 

 the addition of 5 per cent, of aluminium to iron makes the 

 conductivity of the alloy five times worse than iron ; (3) the 

 greatest reduction in conductivity in a given alloy is produced by 

 the first increments of the added element. This is shown in the 

 accompanying diagram, where the specific resistances of some of 

 the alloys examined (deduced from their conductivities), are 

 plotted against the percentages of the added element : the 

 specific resistance of iron alone being shown by the horizontal 

 dotted lines, the upper containing 0-3 and the lower only 

 oi per cent, of carbon and other foreign bodies. The 

 series of fairly smooth curves thus obtained for each alloy are 

 seen to be steepest near their origin, a curious flexure being 



* ScUnti/ic Transactions of the Royal Dublin Society^ vol: 

 ' Researches on the Phy^ical Properties of the Alloys 

 V. F. Barrett, W. Brown and R. .\. Hadfield. 



by 



ParccnCa^es of Added EiemenC. 



found in the nickel steels ; (4) a relationship does appear to 

 exist between the specific heat of the added element and the 

 resistance of the alloy it forms when united with iron. In the 

 diagram the specific heats of the various elements are placed 

 after their names. Thus the specific resistance of an alloy of 

 5^ per cent, of aluminium with iron is seen to be 70 microhms, 

 the same amount of silicon with iron 65 microhms, of manganese 

 with iron 38 microhms, of nickel 27 microhms, and of 

 tungsten 18 microhms; now the specific heats of these 

 elements are, aluminium 0-212, silicon 0-183, manganese 

 0-I22, nickel 0-109, ^"d tungsten 0-035. Those elements 

 having high specific heats, and therefore small atomic or 

 molecular masses, produce the greatest increase in electric 

 resistivity of the corresponding alloy with iron. 



Dividing the inaease in electric resistivity by the percentage 

 of the added metal, we obtain the increase in the specific re- 

 sistance of iron produced by I per cent, of the added element. 



NO. 1695, VOL. 65] 



