May 1 6, 1889] 



NATURE 



63 



in a previous paper of Dr. IJehrend's to possess the consti- 



NH— CH 



I II 



tution CO COH. (6) By oxidation of iso-barbituric acid with 



I I 



NH— CO 



bromine water another acid is obtained, which is found to be 



isomeric with dialuric acid, but differs entirely from that acid in 



properties ; it is therefore termed iso-dialuric acid. From 



its reactions it is shown to correspond to the constitution 



NH-CHOH 



I I /OH 



CO ^"\ OH' It crystallizes in long rhombic prisms contaming 



NH— CO 



a molecule of water of crystallization, which it loses at 

 ioo° C. The yield is very good, 80 per cent, or more 

 of the theoretical. (7) It now only remains to mix this iso- 

 dialuric acid with one equivalent of urea and six equivalents 

 of sulphuric acid, the latter to take up three molecules of 

 water which are eliminated in the reaction between the two 

 former substances. The reaction is complete in the cold in twenty - 

 four hours, or in five minutes if the mixture is gently warmed 

 upon a water-bath. On cooling and adding water, uric acid is 

 precipitated in small crystals, which, on purification, exactly 

 resemble those of natural uric acid. The equation is very 

 readily understood, there being a simple combination of iso- 

 dialuric acid and urea with formation of uric acid and elimination 

 of three molecules of water — 



-^ + 3II2O. 



NH-CHOH NH— C— NH 



! I /OH /NH2 I II 



CO C< + CO< = CO C— NH 



I I ^OH ^NH., I I 



NH— CO ' NH-CO . 



Iso-dialuric acid. Urea. Uric acid. 



Hence the formula of Medicas and Fischer for uric acid may 

 now be considered as finally proved. 



The additions to the Zoological Society's Gardens during the 

 past week include a Purple- faced Monkey {Seinnopithecus letico- 

 prymnus) from Ceylon, presented by Mr. J. H. Taylor ; a Vervet 

 Monkey {Cercopithecus lalaiidii i) from South Africa, pre- 

 sented by Dr. W. K. Sibley ; an Otter {Lzttra vtilgaris) from 

 Cornwall, presented by Mr. Basset ; a Long-eared Owl {Asio 

 olus), Briti>h, presented by the Hon. Eric Thesiger ; a Herring 

 Gull {Lanes argentalus), British, presented by Mrs. Gainsford ; 

 a Yellow-billed Amazon {Chrysalis panatnensis) horn Panama, 

 presented by Lord William Cecil ; two Common Kestrels 

 (Tinnuncuhts alaudarius), captured at sea, presented by 

 Captain Janes ; two Common Rheas {Rhea americana, juv.) 

 from Uruguay, presented by Mr. J. D. Kennedy ; a Black 

 Swan [Cygnus atratus i) from Australia, presented by Mrs. 

 Siemens ; a Long-eared Owl {Asio otus), British, presented by 

 the Rev. F. Hopkins ; two Natterjack Toads {Bufo calamita), 

 British, presented by Master H. Millward ; two Natterjack Toads 

 {Bufo calamita), British, presented by Master A. Smith ; a 

 Bonte-bok {Alcelaphus pygargus i ) from South Africa, de- 

 posited ; a Squacco Heron {Ardea raiioides) from South Europe, 

 three Japanese Teal {Querqnedtila formosa 3 9 9), from North- 

 East Asia, an Amherst Pheasant {Thaumaha amherstice i ), from 

 Szechuen, China, purchased ; two Moor Harriers {Circus 

 maurus) from South Africa, received in exchange. 



OUR ASTRONOMICAL COLUMN. 



The Residuals of Mercury. — In a recent discussion of the 

 perturbations of Mercury {Astronomical Journal, No. 191, April 

 15, 1889), Mr.' O. T. Sherman has arrived at some important 

 and highly suggestive results relating to the residuals. His 

 method ^of determining these appeared in No. 173 of the 



Astronomical Journal, and this process has been employed in 

 obtaining the data given in the article referred to. The values 

 arrived at show a remarkable relation to the heliocentric latitude 

 of the planet, the maximum effect being nearer the solar equator, 

 and the effect decreasing as the latitude increases. Since the lower 

 latitudes correspond to maximum and the higher ones to mini- 

 mum solar activity, the apparent connection of the disturbances 

 of the planet with solar phenomena should also bear some rela- 

 tion to the sun-spot period, and Mr. Sherman gives figures to 

 show that this is the case. The chief disturbances occur in the 

 years when I he sun-spots are increasing in frequency, and it is 

 pointed out that this result is in strict ace )rdance with the 

 retardations of Encke's Comet during perihelion passage. 



It is further stated that " the forces deflecting the planet are 

 sunward when the planet is in that part of space towards which, 

 the sun is travelling, and away from the sun when the planet 

 follows in his path." This, taken in conjunction with the dis- 

 turbances of Encke's Comet, seems to Mr. Sherman " to indicate 

 a considerable amount of matter coming to the sun from space. 

 If so, its place of meeting with the matter coming from the sun 

 should abound in collisions, and display local spectra showing 

 bright lines. Our knowledge of the zodiacal light is fully ii> 

 accord with such a supposition." 



If the more detailed investigations of the residuals, which it 

 is intended to make when more-observations have been collected^ 

 confirm the results already obtained, we may look for a consider- 

 able advance of our knowledge, especially of the nature of the 

 solar surroundings. Already the residuals clearly admit of ex- 

 planation by supposing that the sun, with its meteoritie 

 surroundings, in the form of the corona and the zodiacal light, is 

 moving with considerable velocity through a meteoritic plenum. 

 In that case the planet would encounter most meteorites when 

 on the advancing side of the sun, and it would obviously be more 

 retarded there than elsewhere. 



The apparent relation to the sun-spot period is of great interest 

 in connection with the meteoritic theory of the formation of sun- 

 spots. According to this theory, there should be most meteorites- 

 in the solar surroundings at maximum spot period, and greater 

 disturbances of the planet at that period would therefore be ex- 

 pected. The collisions between tlie two sets of meteorites would 

 further produce the spectroscopic phenomena associated with the 

 zodiacal light — namely, the appearance of a line near wave-length 

 558, which has been ascribed to manganese. It seems probable 

 that the variability of this spectrum which has been suspected by 

 Mr. Sherman (letter to Mr. Lockyer, quoted in Roy. Soc. Proc.^ 

 vol. xlv. p. 248) may also subsequently be shown to be connectedi 

 with the sun-spot period. 



Right Ascensions of North Circumpolar Stars. — 

 Prof. T. H. Safford, Field Memorial Professor of Astronomy at 

 Williams College, Mass., has just published a very useful piece 

 of woik in the shape of a Catalogue of North Polar Stars. 

 This Catalogue, which is a first instalment of a more extensive 

 one, the observations for which are now in progress, has beea 

 constructed by Prof. Safford in order to strengthen what he felt 

 to be the weak point of all the standard Catalogues, viz. the 

 right ascensions of Polar stars. It was also a consideration with 

 him that it would be easier to take account of instrumental cor- 

 rections if a more extended list of Polars were generally used 

 than has been the custom. These stars are also of importance 

 in the study of proper motion?, since their early observations^ 

 are accurate. 



The observations for this Catalogue were made at the Field 

 Memorial Observatory, and not at the Hopkins Observatory of 

 Williams College, and the meridian circle with which they were 

 made was a fine one of 4^ inches (French) aperture, by Repsold. 

 The observations were made at first by eye and ear, but a fillet 

 chronograph was used in 1887 and 1888. Prof. Safford's inten- 

 tion throughout was to make his Catalogue a differential one ; 

 the stars he has relied upon for his instrumental corrections, 

 being those of Publication 14 of the Astronomische Gesellschaft, 

 which lie within 10° of the Pole. Besides the catalogue itself, 

 which contains 261 stars, of which just 200 are within 10° of the 

 Pole, a very important part of the work is the discussion of the 

 right ascensions, with a view to clearing up certain points as to- 

 mode of observation, as well as to find the weights and system- 

 atic corrections necessary for combining this series with others. 

 The result of this discussion is to show that it tends to greater 

 accuracy to base a catalogue of Polar R.A.'s on standard places 

 in all hours of right ascension rather than on double transits 

 alone ; that the eye-and-ear method should be used as the stan- 



