306 



NATURE 



{Jan. 26, 1888 



If my contention in this and previous papers be correct, that 

 residual affinity thus plays a far more important part than has 

 hitherto been supposed, and that it must be taken into account 

 in all discussions on valency, it folio a^s of necessity that our 

 views regarding the constitution of the majority of compounds 

 at present rest upon a most uncertain basis : the constitution of 

 the paraffins, of the benzenes, and of the haloid co.npounds and 

 alcohols derived from the hydrocarbons of these series, may be 

 regarded as determined vi^ith a degree of precision almost 

 amounting to certainty ; but in the vast majority of other cases 

 we have as yet no secure method of arriving at conclusions 

 which in any sense approach finality. There can belittle doubt 

 that in framing our modern conceptions of valency we have 

 been too much influenced by the graphic symbols which have 

 been so widely made use of. In the future it will be necessary 

 to attach a more liberal interpretation to the facts, and it may be 

 hoped that it will some day be pos5ible also to take into account 

 differences depending on the relation of the different forms of 

 matter to the pervading medium. 



The properties of compounds being demonstrably dependent 

 on the intramolecular conditions, it is difficult for a chemist to 

 resist the feeling that the peculiarities manifested by the different 

 elements are also very probably the outcome of differences in 

 structure ; such an assumption in:leed affords at present ap- 

 parently the only explanation that can be given of the relationship 

 manifest between different elements when these are classified in 

 groups of " homologues " in accordance with the suggestion 

 originally made by Dumas, which has now found full expression 

 in the so-called periodic system of classification. There 

 appears to be an increasing weight of evidence to favour the 

 assumption that the influence exercised by compounds in cases 

 of chemical change is local in its origin : that it is exercised 

 more by a particular constituent or constituents — in particular 

 directions, in fact — than by the molecule as a whole. The sug- 

 gestion above made that ' ' affinity " acts in particular directions in 

 elementary atoms, and perhaps with different degrees of freedom 

 in various directions, is therefore but an extension to elements 

 of what is more or less generally recognized as the case in com- 

 pounds. Some such hypothesis is certainly required to account 

 for the existence of allotropic modifications both of non-metals 

 and of metals ; for the remarkable changes in magnetic and 

 other properties which iron undergoes with change of tempera- 

 ture ; for the different values of the dielectric constant — along 

 the several axes in sulphur crystals ; for the difference in electric 

 conductivity of bismuth in two different directions in bismuth 

 crystals ; for the existence of planes in crystals in which cleavage 

 takes place with special readiness, &c. — all these are instances 

 which apparently afford evidence of atomic dissymmetry. May 

 not valency after all depend — not in the number of "charges" 

 carried by the atom, but — on the number of directions in which 

 the ever-present " lines of force " are free to act ? 



WORK OF THE KEW OBSERVATORY IN 

 1887. 



nrilE Annual Report of the Kew Committee, just issued, shows 

 •^ that the activity of the staff of the Kew Observatory is still 

 well sustained, and the various departments devoted to observa- 

 tions — magnetic, meteorological, and solar — verification of 

 scientific apparatus of various kinds, rating of timepieces, and 

 experiment, all show a considerable turn out of work. In 

 addition to the regular periodical magnetical observations, 

 the main results of which are given in a concise form in the 

 appendixes, assistance was rendered to Profs. Riicker and 

 Thorpe in respect to their valuable magnetic survey of Great 

 Britain, M'hich we are glad to learn they have now completed, 

 after having devoted the greater portion of their vacations to 

 the task for the la=t four years. The labours of the Krakatao 

 Committee of the Royal Society, the Magnetic Committee of 

 the British Association, the late Prof. Balfour Stewart, and 

 other investigators, have also been supplemented by aid afforded 

 by the Kew staff. 



The meteorological staff have during the year recorded, 

 principally on behalf of the Meteorological Council, who defray 

 the expenses attendant on the work, some 57,126 observa- 

 tions averaging over 150 per diem ; the resulting monthly and 

 annual means are, by permission of the Council, published as 1 

 appendixes. 



The multiplication of Observatories engaged in solar photo- j 



graphy at home and abroad having rendered unnecessary the 

 co-operation of Kew in that branch of science, so energetically 

 carried on there by the present Chairman, Mr. De la Rue, and 

 the late Prof. Balfour' Stewart, twenty years ago, the photo- 

 heliograph has only been employed of late years as an ordinary 

 telescope, by means of which the counting of new sunspot 

 groups is continued after Schwabe's method. 



An appendix shows that during the last year 44 new groups 

 were catalogued, and that on 60 days out of 180 days of 

 observations the sun's surface was free from spots. 



Under the heading "Experimental Work" we find a good 

 deal of attention has been devoted to the photography of high 

 cirrus clouds simultaneously from two points, with the view of 

 determining their position and motions ; and to the question of 

 the proper construction of black bulb thermometers ; and also to 

 preparatory operations with the Indian Government pendulum 

 apparatus, prehminary to repeating the observations made at the 

 Observatory by Basevi, Heaviside, and Herschel. 



There is a long list of various instruments compared and 

 certified during the year in the verification department, which 

 shows that nearly 14,000 articles belonging to one or the other 

 of twenty-seven different classes have undergone treatment ; as 

 instruments newly brought within the influence of the verifier, 

 attention is di-ected to range-finders for the use of the Army 

 and Navy, telescopes of the Admiralty pattern, and surveying 

 aneroids. 



The popularity of the Kew certificates, a^ to the time-keeping 

 of watches, shows that the demand for a guarantee as to the 

 accuracy of performance of a watch other than the maker's name 

 actually exists, and no less than 510 watches and 27 marine 

 chronometers have been submitted to the rating department 

 since the last report was issued. 



An appendix showing the behaviour of the best of the watches 

 during the test is given, and it is found that places in this list 

 are being strongly contested for by watch manufacturers, as the 

 blue ribbons of the trade. In consequence of the growth of the 

 work done at Kew, steps have been taken to obtain the per- 

 mission of Her Majesty's Chief Commissioner of Works and 

 Public Buildings to enlarge the Observatory, which at present 

 remains almost in the same condition as it stood 130 years ago 

 when originally erected as His Majesty George III.'s private 

 Observatory at Richmond. 



THE TOTAL ECLIPSE OF THE MOON, 

 JANUARY 2%. 



T3Y the kindness of the Astronomer Royal for Scotland, Mr. 

 Gledhill, of Mr. Crossley's observatory at Bermerside, and 

 Mr. Stothert, all of whom took part in the observation of the 

 eclipse of October 4, 1884, we are enabled to give Prof. Struve's 

 times and position-angles for the stars that will be seen to be 

 occulted by observers stationed at Edinburgh, Halifax, and 

 Bath. A comparison of these tables will enable intending 

 observers in other parts of England to form a sufficieniy correct 

 list for their own locality. 



The fol 'owing ten stars, not included in the list given in 

 Nature for January 19, will be occulted as seen from Edin- 

 burgh : — 



Star No, 106 is of mag. 9-3 ; No. 129, 9*5 ; No. 206 is of the 

 loth magnitude ; the others are all of the nth magnitude. 



Edinburgh. 

 Lat. = 55° 57' 23" ; Long. = 3° 10' 54" W. 



Disappearances. Reappearances. 



Star's Mag. Angle. G.M.T. Star's Mag. Angle. G.MT. 



No. o h. m. No. o h. m. 



II ... 94 ... 10 24-3 108 ... Q-^ ... ^^^ ... 10 26-0 

 10 ... 116 ... 26-9 

 135 ... 272 



No. 

 152 ... II ... 94... 1024-3 108... 9-3 --• 333 



150 ... 10 ... 116 ... 26-9 87 ... II ... 259 ... 260 



142 ... 10 ... 135 ... 272 103 ... II ... 226 ... 28-5 



148 ... 10 ... 57,.. 278 106... 9-3 .. 216 ... 29-8 



129... 9-5 ... 173 ... 280 91 ... II ...290... 30-3 



