350 



NATURE 



\Angtist 12, li 



Reasons are given for adopting the formula of scandium 

 oxide as ScnO,, and the atomic weight of scandium is deter- 

 mined to be 44"o (mean of four closely-agreeing results). Scan- 

 dium is undoubtedly identical with Mendelejeff 's ekabor. 



The specific heat of beryllium has been determined by 

 Nilson and Pettersson. Between o° and lOO" the specific heat 

 is 0'4246 ; between o" and 300°, o'5o6o. These chemists ha\e 

 likewise made a new determination of the combining weight of 

 beryllium, and find it to be 4'55, which is a very little less than 

 the number found by jirevious observers. They think that the 

 atomic weight of beryllium is undoubtedly I3'55, and not g'l, 

 as generally supposed ; oxide of beryllium is therefore Be.,0 j, 

 and this metal is not to be placed, in Mendelejeff's system', as 

 the first member of the magnesium group. Neither can beryl- 

 lium form the first member of the aluminium group, as suggested 

 by Lothar Meyer. Nilson and Pettersson detail many facts which 

 lead them to reg.ird beryllium as the first member of tlie group of 

 cerite and gadolinite metals, which comprises the metals, Be, .'^c, 

 Y, La, Ce, Di, Tr, Y„, Y^, Soret's x, Er, Tu, Yb. The paper 

 contains many most important chemical and physical data con- 

 cerning the salts of the metals of this group. 



From the specific heats of the oxides of beryllium, scandium, 

 gallium, indium, and aluminium, the specific Leat of oxygen in 

 combination is deduced by Nilson and Pettersson as being 2^3 to 

 3'i ; the mean specific heat of oxygen in combination is 4'o; 

 the oxides named are therefore somewhat anomalous. 



The "molecular volume," i - , "^"le'^^^" "'^'a'^t of gas, ^^ 

 sp. gr. of solid 

 the various molecules of water of hydration has been recently 

 shown by Thorpe and Watts to vary in the magnesium group of 

 sulphates ; Nilson and Pettersson obtain nearly the same number 

 (S'S) as representing the mean volume of each water-molecule 

 in the sulphates of yttrium, erbium, and ytterbium ; but a some- 

 what larger number (11 '5) for the mean volume in the sulphates 

 of cerium, lanthanum, and didymium. 



PHYSICAL NOTES 



In liquids small particles often show dancing motions under 

 the microscope, and similar motions have been attributed to 

 diist-particles in air, and accounted for by the shock of molecules 

 with the particles. In a recent paper treating fully of the move- 

 ments of very minute bodies (Mioich. Bei:, 1S79, p. 3S9) Herr 

 Nageli calculates from data of the mechanical theory of gases 

 as to the weight and number and collisions of molecules, the 

 velocity of the smallest fungus-particles in the air that can be 

 perceived with the best microscopes, supposing a nitrogen or 

 oxygen molecule to drive against them. It is, at the most, as 

 much as the velocity of the hour-hand of a watch, since these 

 fungi are 300 million times heavier than a nitrogen or oxygen 

 molecule. The ordinary motes would move 50 million times 

 slower than the hour-hand of a watch. Numbers of the same 

 rnagnitade are obtained for movements of sm.all particles in 

 liquids. In both cases a summation of the shocks of different 

 molecules is not admissible, as the movements are equably dis- 

 tributed in all directions. Ilerr Nageli therefore disputes the 

 dancing motion of solar du^t-particles, and attributes the 

 Browniau molecular motion to forces active between the surface- 

 molecules of the liquid and the small particles ; but he does 

 not say how he conceives of this action. 



The absorption of heat-rays by powders has been lately in- 

 vestigated by Herr van Deventer (Inaiig. Diss. LeiJ., 1S79, p. 

 78, or WicJ. BcihL, 6) without use of any binding material. 

 Under a copper cube kept at 100° was brought a thermo-element 

 consisting of a brass plate, on the lower side of which was 

 soldered a piece of bismuth and antimony (parallelopiped shape). 

 On the plate was strewn the powder to be examined. A second 

 similar element, with thermo-element lampblacked, served for 

 control. Briefly, the results were these : (i) Powdered substances 

 in the same physical state have different absorptive power; (2) 

 this depends on the thickness of the absorbing layer: each 

 powder has its maximum absorption layer ; (3) quite comparable 

 values for the absorption cannot be had, as the thickness of the 

 powder layer cannot be exactly determined ; (4) the divergences 

 proved in Tyndall's results with different binding materials are 

 attributed to his not having taken into account the maximum 

 emission layer ; (5) whether the binding material affects .absorp- 

 tion, and if so, how, can be demonstrated by the author's method 

 (the element being painted over with the liquid holding the 



powder in suspension) : but experiments are here wanting; (6) 

 the author's series of powders arranged according to absorptioa 

 is quite different from Tyndall's emission series. 



Dr. Puluj observes that if an electric radiometer is worked 

 for some minutes and then the circuit is broken, a reversed 

 motion is immediately set up, which continues for four or five 

 minutes with an enormous rapidity. This lie explains by 

 assuming that there are really two actions tending to produce 

 rotation : the electric reaction between the vanes and the 

 molecules, and the heating of the metallic side of the vanes ; 

 that these two actions oppose one another, but that at small 

 pressures, such as the high vacua, the electrical forces are in 

 excess. When however they are brought to an end the heat- 

 forces assert themselves, producing the opposite rotation. 



From recent experiments (described in IV^ied. Ann., No. 7) 

 Herr Heitz concludes that the kinetic energy of the electric 

 current in i cubic millimetre of a copper conductor, traversed by 

 a current of unit electromagnetic density, is less than o'ooS milli- 

 gramme-millimetre. As the kinetic energy is equal to half the 

 mass multiplied by the square of the velocity, the mass of the posi- 

 tive electricity in i cub-mm. is < °°° '""" . E.i'.,\iv — iram., 



v" 

 10 mm., &c., the mass of the positive electricity <0'0o8mg., 

 <0"oooo8mg., &c. The limits here assigned, however, are 

 exceeded where the densities of the electricity in the materials 

 used are as their conductivitie-;. (The experiments were made 

 both with straight wires and with spirals, the former giving the 

 more reliable results.) 



The results of theory regarding stationary vibrations of water 

 are, in a recent paper (IVied. Ann., No. 7) by Plerr Kirchhoff 

 and Herr Hansemann, compared with those of experiments in 

 which a prismatic glass vessel, whose vertical cross-section con- 

 sisted of two straight lines meeting at a right angle and equally 

 inclined to the vertical, formed part of a pendulum, and was 

 vibrated by electromagnetic means about that angle as axis. In 

 tlie Journal de Pltysiijue (June) M. Lechat studies the surface 

 vibrations of a liquid in a rectangular vessel, a small vertical 

 rod having been adjusted to any point of the surface, and vibrated 

 in the direction of its length by an electro-magnetic an-angement. 

 The resultant forms were thrown on to a screen by means of a 

 reflected beam of light. 



In a recent paper to the Belgian Academy (Bull., No. 5) 

 Abbe Spec contends that the spectral line D3, with wave-length 

 about 588, observed in the chromosphere and protuberances, and 

 assigned to a hypothetical body, helium, which some suppose to 

 have a still more simple molecular constitution than hydrogen, 

 probably belongs in reality to this gas. As to its non-reversi- 

 bility, he considers that at a very small distance from the chromo- 

 sphere the solar hydrogen may be so' far cooled as to be 

 comparable to that \\hich we manipulate, and so, unable to 

 extinguish waves which it can no longer produce, just as a 

 stretched cord loses the property of vibrating in sympathy if its 

 tension have been altered. 



Pursuing his researches on the welding of solid bodies by 

 pressure, M. Spring has subjected to various strong pressures 

 (up to 10,000 atm.) more than eighty solid pulverised bodies; 

 this was done in vacuo, and in some cases at various tempera- 

 tures. The results are highly interesting. All the crystalline 

 bodies proved capable of welding, and in the case of bodies 

 accidentally amorphous the compressed block showed crystalline 

 fracture ; crystallisation had been brought about by pressure. 

 Softness f.avours the approximation of the particles and their 

 orientation in the direction of the crystalline axes. The amor- 

 phous bodies, properly so called, fall into two groups, one of 

 substances like wax [ciroid bodies), which weld easily, the other 

 of substances like amorphous carbon (aciroid bodies), which do 

 not weld. The general result is that the crystalline state favours 

 the union of solid bodies, but the amorphous state does not 

 alw.ays hinder it. M. Spring says the facts described do not 

 essentially differ from those observed when two drops of a liquid 

 meet and unite. Hardness is a relative, and one may even say 

 subjective, term. Water may appear with a certain hardness to 

 some insect--, and if our bodies had a certain weight we should 

 find the pavement too soft to bear us. Again, prismatic sulphur 

 is changed by compression to octahedric sulphur ; amorphous 

 phosphorus seems to be changed to metallic ; other amorphous 

 bodies change their state, and njixtures of bodies react chemically 

 if the specific volume of the product of the reaction is smaller 

 than the sum of specific volumes of the reacting bodies. In all 



