June 6, 1901] 



NA TURE 



129 



are not explained by the theory of Wislicenus and 

 van 't Hoff {Journ. Prac. C/iem. 1895, [-\ '''> 365-372) ; 

 but, as was shown in the celebrated controversy with 

 Fittig {Liebi^s Atin. 1892, cclxxii, 1-99) over the brom- 

 additive products of angelic and tiglic acids, the condi- 

 tions of the experiment play such an important part in 

 determining the nature of such reactions that the bearing 

 of the results on the validity of the theory must be ac- 

 cepted with a certam amount of reservation. The 

 matter is still the subject of discussion ; for the present 

 we can only quote the words of an illustrious chemist, 

 who said that " unter alien sonst vorgebrachten 

 Erklarungs-versuchen lehrt kein einziger auf gleich ein- 

 fach und gleich umfassende weise die beobachteten That- 

 sachen verstehen." 



Wislicenus has of late been engaged in the application 

 of the theory of spacial relations to the formation of ring 

 compounds, his synthesis of cyclo-pentanone from the 

 calcium salt of adipic acid serving as a starting point in 

 the preparation of the simplest five-ring compounds. 

 Especial interest attaches to the investigation of suberone, 

 which was shown to be a seven carbon ring ; for the 

 theoretical consideration of von Baeyer {Bi-r. 1885, 

 xviii, 2277), in addition to those already referred to, 

 would make us regard a seven carbon ring as unstable 

 as a four. 



Wislicenus is one of the forty foreign members of the 

 Royal Society, and was awarded the Uavy medal in 1898. 

 Still working with all the vigour of an enthusiast, lectur- 

 ing both in summer and winter at eight o'clock, making 

 frequent tours through the research laboratories with 

 his note-book and cigar, and listening patiently to the 

 "Auslander" who bury their unsuccessful experiments 

 in the mysteries of the German language, he attracts 

 students of every nationality, for he has a personality 

 which makes its influence felt ; and those who have 

 enjoyed the privilege of working under him have lost 

 none of their respect for a distinguished teacher in their 

 appreciation of his kind hospitality and generous spirit. 



TBE CENTENARY OF THE DISCOVERY OF 

 CERES. 



A HUNDRED years have passed since Piazzi, at 

 Palermo, opened a new era in observational 

 astronomy by the discovery of the first of the many 

 small planets that circulate between the orbits of Mars 

 and Jupiter. This welcome, but not unexpected, addition 

 to the known members of the solar system gave an in- 

 creased interest to the routine of observation, supplied 

 fresh reasons for the preparation of accurate star 

 catalogues, and quickened the researches of practical , 

 astronomy, a little overshadowed by the brilliancy of the 

 results won on the physical side by the French mathe- 

 maticians of the last century. It is true that within the 

 space of time which has elapsed since Piazzi used to such 

 good purpose the altazimuth of Ramsden, the history of 

 astronomy has had to record, not only the growth, but also 

 the decrease, of interest which has been a consequence 

 of the rapid discovery of similar objects. Nevertheless, 

 Piazzi's discovery was fortunate and fructiferous, and we 

 willingly associate ourselves with those of his countrymen 

 who have recently sought to do honour to his memory and 

 to demand due recognition for his services. We are 

 reminded, in a recent number of Memoric delta Societa 

 degli Spettroscopisti Ilaliaiii, that though the story of the 

 discovery of Ceres may have been frequently told and is 

 very \yell known, yet there are features connected with it 

 of which we may well be reminded. For eight years with 

 untiring diligence did Piazzi patiently work, before he 

 made the discovery which has rendered his name a house- 

 hold word and endeared his memory among his country- 

 men. Doubtless he himself considered his star catalogue 

 NO. 1649, VOL. 64] 



a far greater work, and so posterity will esteem it ; but the 

 renown that attaches to such a discovery is immediate 

 and, in a sense, abiding. To appreciate fully what it 

 meant at the time, we must recall the confidence and the 

 agitation which were connected with the so-called Bode's 

 law. The evidence such a formula offered of the existence 

 of an undiscovered planet may not appear now very con- 

 vincing, but the confidence with which it had been 

 received had been strengthened by the comparatively 

 recent discovery of Uranus, and astronomers, among 

 whom may be reckoned Schrteter and De Zach, were 

 banded together with the firm determination to discover 

 the missing link in the chain of planetary distances. 

 Piazzi, according to Grant, stood outside this company of 

 eager astronomers, but the late Admiral Smyth, who had 

 exceptional information from his personal acquaintance 

 with Piazzi, gives him a place in the circle. In any case 

 it was due to systematic work diligently pursued by the 

 Palermo astronomer that the prize was won. 



But, as pointed out by Prof. Angelitti and others 

 who have taken part in the centennial celebrations, the 

 indirect results of the discovery have far outweighed the 

 immediate. Among these may be reckoned the earlier 

 publication of the "Theoria Motus"of Gauss, and especially 

 those chapters which deal with the computation of an 

 elliptic orbit from observations that embrace only a short 

 interval of time. This classical work has remained for a 

 century, the model on which all similar calculations have 

 been based. Alterations of detail have been introduced 

 from time to time bearing upon special parts of the work, 

 but practically the method followed to-day is the method 

 that Gauss evolved to rescue and identify the discovered 

 planet of Piazzi from the stars by which it is surrounded 

 and which it so much resembles. It is well known that 

 Ceres, as the small planet was called, was followed by 

 Piazzi only from January i to February 11. Oriani 

 and Bode, to whom Piazzi forwarded his observations, do 

 not appear to have seen the planet in the first year of its 

 discovery, and Gauss' researches and the success that 

 attended them rest entirely on the labours of the original 

 discoverer. 



It is not out of place to recall how the discovery of 

 small planets and the eagerness with which they were 

 sought in the middle of last century gave a great impetus 

 to the construction of accurate maps of the heavens. The 

 Berlin charts led to the ready recognition of Neptune, 

 while the ecliptic charts of Hind, of Peters, of 

 Chacornac and of a host of others who engaged in the 

 work, added greatly to our knowledge of the configuration 

 of the heavens and the arrangement of the stellar universe. 

 And it must be remembered that one of the first, if not 

 the first, valuable application of photography to astronomy 

 had for its aim the rapid delineation of such charts 

 originally devised for the detection of small planets. 

 To the fruitfulness that has followed this peculiar direction 

 of thought it is not necessary to refer more particularly, 

 but it would not be difficult to show that the discovery of 

 small planets, originating in the small observatory of 

 Palermo, has exercised an enormous influence on the 

 methods of observation now so generally pursued. 



We need do no more here than barely refer to the 

 important part that the group of small planets has played 

 in the oldest of old problems, that of the distance of the 

 Sun. Let the bulky volumes that Sir David Gill has sent 

 from the Cape speak of the work that small planets have 

 furnished to the astronomer in this chapter of his science. 

 And now, practically a century after Piazzi taught us how 

 the space between Mars and Jupiter is crowded with 

 cosmical matter, we find astronomers of all nations 

 cooperating on the systematic observation of one of 

 these small bodies, only intent upon bringing the new 

 material to aid more efficiently in the serivce of the old. 

 Small planets have played, and in the future will continue 

 to play, a part in the onward progress of astronomy, and 



