May 7, 1903] 



NA TURE 



23 



live reading of a dimensional formula by enclosing the sign 

 of equality in square brackets thus : — 



[force][ = ][M][L][T-^] 

 and the reading of it as a physical identity or equivalence 

 thus : — 



[force] ^tM][L][T-»]. 

 The dimensional relation M = L'T~- derived from the law 

 of gravitation is examined at length. This relation, com- 

 bined with the demand for the complete correlation of all 

 dynamical units, is shown to require the adoption of the 

 convention 



[L][ = ][T][ = ][M]. 



This result is interpreted by (i) above. Systems of dimen- 

 sions are next discussed, with the aid of illustrative tables, 

 and it is shown that by employing different physical laws 

 as bases many different systems may be constructed. — Mr. 

 R. J. Sovtfter read a note on dimensions of physical quanti- 

 ties. Mr. Ravenshear has shown that any physical quantity 

 is expressible in terms of the dynamical quantities L, M 

 and 1', in different ways, but that all the various ways are 

 ( onnected with one another by an index law. One in- 

 terpretation of this is that the dynamical factors are com- 

 plete in themselves. They express change-ratios, and have 

 no qualitative significance. ;u, fc, 7, &:c. do not contain 

 dynamical factors, but carry with them the physical quali- 

 ties or characteristics of the quantities associated with them. 

 Any physical quantity, on this hypothesis, is expressible as 

 ' =N(L)")(7, where N is a mere number, (D") is a dynamical 

 factor indicating a quantitative measurement process, and 

 (/ is a quality factor of the nature of Q. 



Geological Society, Apiil 8.— Mr. J J. H. Teal), F.R.S., 

 i( e-president, in the chair. — On the probable source of some 

 the pebbles of the Triassic Pebble-Beds of South Devon 

 id of the midland counties, by Mr. O. A. Shrubsole. 

 i he author describes the Budleigh-Salterton Pebble-Beds. 

 1 he supposition is natural that Devonian rocks were once 

 represented either in the Calvados district or in some region 

 in the same drainage-area as that which has supplied the 

 Ordovician element. The Grfes de May of Normandy 

 appears capable of furnishing abundant material, not only 

 for the Ordovician pebbles of the Budleigh-Salterton Pebble- 

 Bed, but also for a great deal more. A list of species 

 common to the Gr^s de May, of May itself, and the Bud- 

 leigh-Salterton deposit is given. The author is struck with 

 the resemblance of the Midland Bunter to that of Devon. 

 Strong family likenesses subsist between certain specimens 

 in the northern and southern Bunter and some of the un- 

 disturbed rocks of Normandy. A list of fossils from the 

 Midland Bunter contains three southern forms. Fourteen 

 out of twenty of the Drift and Bunter fossils are found at 

 Budleigh-Salterton and in Normandy. — Note on the occur- 

 rence of Keisley-Limestone Pebbles in the Red Sandstone- 

 Rocks of Peel (Isle of Man), by Mr. E. L. Gill. Pebbles 

 of a coarsely-crystalline, greyish-white, mottled limestone, 

 collected by Prof. W. Boyd Dawkins from the conglomer- 

 ates at Whitestrand, contain the following fossils : — Illaetms 

 Howmanni, var. brevicapitattts, Primitia Maccoyi, Orthis 

 <r.lli^rawma, O. iestudinaria. O. biforata, Rafinesquina 

 ilcltoidca, PlectambonUes quinquecostata, Atrypa expansa, 

 llyatclla Portlockiana, Dayia pcntagonalis, Platyceras 

 VL-risiniile, Stenopora fibrosa, and crinoid-stems. This 

 assemblage of fossils corresponds strikingly with that of 

 the Keisley Limestone, and it is therefore concluded that 

 the pebbles have been derived from that rock. 



Dublin. 

 Royal Irish Academy, A ril 27.— Prof. Atkinson, presi- 

 dent, in the chair. — Observations on the temperature of 

 the subterranean organs of plants, by Dr. Henry H. Dixon. 

 i'revious experimenters on the temperatures of plants have 

 • nfined their investigations to the aerial organs. Dutrochet 

 ione experimented with subterranean organs, but only 

 liter removal from the soil. He believed that these organs 

 are at the same temperature as their surroundings. From 

 the experiments described in this paper we may infer 

 iiat (i) subterranean organs, e.g. bulbs, like aerial organs, 

 iv have' during active growth a higher temperature than 

 neir surroundings. The amount of this temperature-eleva- 

 lion rtiay be as much as 006° C. (2) After the period of 



NO. 1749. VOL. 68] 



active growth is passed, this temperature-elevation is no 

 I longer noticeable. (3) There is no true indication of a 

 j spontaneous periodic diurnal rise in the temperature of 

 subterranean organs, such as has been recorded by other 

 writers for aerial organs. A periodic diurnal rise may 

 i occur owing to the periodicity of the temperature of the 

 j surroundings, which in its turn may cause an increase 

 j in the metabolic activity of the plant, and so give rise to 

 a periodic elevation of temperature. (4) In the less massive 

 subterranean organs the temperature rise is not sufficient 

 to make itself appreciable above the fluctuations of the 

 surroundings and the errors of experiment. The paper also 

 contains an account of the errors affecting the thermo- 

 electric method of determining plant temperatures, and also 

 of some suggestions with a view to minimising them. 



Paris. 

 I Academy of Sciences, April 27.— M. Albert Gaudry in 

 • the chair. — ^The president announced the death of M. de 

 Bussy, member of the section of geography and naviga- 

 tion. — On the radiation of polonium and on the secondary 

 radiation which it produces, by M. Henri Becquerel. The 

 radiation of polonium differs from that of radium by the 

 absence of rays resembling the kathode rays. The chief 

 portion of the polonium rays possesses identical properties 

 with the a-rays of radiuin and the canal rays of Goldstein. 

 Up to the present these have been the only polonium rays 

 known, but the author has recently recognised the existence 

 of other rays, distinguished by their powers of penetration. 

 These penetrating rays produce effects which are in every 

 way comparable with the penetrating rays of radium 

 filtered through a considerable thickness of metal. Hence 

 it would appear that of the three distinct kinds of radiation 

 possessed by radium, polonium possesses only two, the part 

 missing being that of a kathodic nature. — The eclipse of the 

 moon of April 11 at the Observatory of Marseilles, by 

 M. Stophan. — Observation of the partial eclipse of the 

 moon of April n at the Observatory of Bordeaux, by 

 M. G. Rayet. The atmospheric conditions were extremely 

 favourable for observations ; one peculiarity noticed in the 

 eclipse was that whereas in ordinary eclipses the entire 

 disc of the moon can be seen during the greater part of the 

 eclipse, in this case the eclipsed part of the moon had com- 

 pletely disappeared. This was noticed both in the eye 

 observations and the photographs. — The catalytic decom- 

 position of alcohols by finely divided metals, allyl and benzvl 

 alcohols, secondary and tertiary alcohols, by ^LM. Paul 

 rabatier and J. B. Senderens. It has been shown in 

 previous papers that metallic copper, prepared by the re- 

 duction at a low temperature, reacts with the primary 

 alcohols, giving the aldehyde and free hydrogen. This re- 

 action has now been extended to allyl, benzyl, isopropyl and 

 other secondary alcohols. Allyl alcohol gives a 50 per cent, 

 yield of propyl aldehyde, and benzyl alcohol gives hydrogen 

 and the aldehyde. Secondary alcohols give hydrogen and 

 j the corresponding ketone in good yields, provided that the 

 ; temperature does not rise too high. Tertiary alcohols split 

 up into water and ethylene hydrocarbons. Reduced nickel 

 gives rise to similar reactions, but there is a tendency to 

 further decomposition, and the yields are npt so good. — 

 M. Noether was elected a correspondant inM^he section of 

 geometry in the place of the late M. Fuchs.— On the observ- 

 ation of the eclipse of the Moon of April ii, by M. P. 

 Puiseux. The extreme blackness of the eclipsed portion 

 of the moon, noticed by other observers, was also in evidence 

 at Paris.— The eclipse of the moon of April 11-12, by 

 M. A. Kannapell. The results of observations made at 

 the Observatory of the Faculty of Sciences at Paris. — On 

 I the deadening of the tremors of the ground. The applica- 

 i tion of a bath with a thick layer of mercury, by M. Maurice 

 Hamy. A study of the theory of the use. of mercury baths 

 in preventing oscillations. An apparatus designed to carry 

 out the conditions indicated by these researches was in- 

 stalled in the neighbourhood of a 4 h.p. gas engine with 

 very satisfactory results.— The calculation of the time and 

 height of high tide by means of harmonic constants, by 

 M. Rollet de I'Isle. — Observations of the sun made at the 

 Observatory of Lyons with the 16 cm. Brunner equatorial 

 during the first quarter of 1903, by M. J. Guillaume. The 

 observations are given in three tables showing the number 

 of spots, their distribution in latitude, and the distribution 



