June 4> 1891] 



N'AtURE 



115 



into about twenty times its weight of fuming sulphuric add at a 

 temperature of about 20°-25°. The fuming acid should contain 

 at least 80 per cent.of sulphuric anhydride, and the temperature 

 should be so controlled that it never exceeds 30° during the pro- 

 cess of adding the mixture. The yellow solution thus obtained 

 yields instantly the blue coloration due to indigocarmine on re- 

 moving the large excess of sulphuric anhydride by the addition 

 of ordinary oil of vitrol, sulphur dioxide being evolved. Upon 

 further diluting with ice and addition of common salt (indigo- 

 carmine being more difficultly soluble in salt solutions than in 

 pure water) the colouring-matter is precipitated, and may be 

 readily isolated. The product thus obtained is found to consist 

 of pure indigocarmine. The tints obtained with this product are 

 vastly superior in beauty and clearness to those obtained with 

 even the better kinds of commercial indigocarmine, on account 

 of the higher degree of purity attained by this mode of prepara- 

 tion. The chemical changes occurring during the process 

 appear to be as follows. The first product of the action of 

 fuming sulphuric acid upon phenylglycocoU appears to be the 



COSO3H 

 sulphonic acid of indoxyl sulphate, SO3H— CeHg/' \CH . 



NH 



This substance, however, is unstable, and decomposes upon 

 the removal of the excess of SO3 into indigo disulphonic acid, 

 sulphur dioxide, and water, probably according to the following 

 equation — 



COSO3H 



2SO3II— C6H3<(' "^CH = 2SO2 -I- 2H2O -h 

 NH 



SO3H-C6H3/ >C = C< >CgH3-S03H. 



Of course the most important point of commercial interest about 

 a new reaction is the yield, and m this respect Dr. Heymann is 

 very fortunate, for already 60 per cent, of the theoretical has 

 been attained. The process has consequently been patented by 

 Messrs. Bayer and Co., and appears likely to become a very 

 successful one. 



The additions to the Zoological Society's Gardens during the 

 past week include a Water Buck [Cobiis ellipsiprymnus ? ), a 

 Leopard (Felis fardus), two Vulturine Guinea Fowls {Numida 

 vitltitrina), two Mitred Guinea Fowls {Numida mitratd) from 

 East Africa, presented by Mr. G. S. Mackenzie, F.Z.S. ; a 

 Peregrine Falcon {Falco peregrinus) from Scotland, presented 

 by Mr. Thomas C. Smith ; a Mountain Ka-Ka {Nestor notabilis) 

 from New Zealand, presented by Mr. Herbert Furber ; a Grey 

 Squirrel {Sciurus griseus), a Squirrel {Sciurus sp. inc.) from 

 North America, a Ducorp's Cockatoo {Cacatua ducorpsi) from 

 the Solomon Islands, presented by Mr, Nicholas O'Reilly ; two 

 Ravens {Corvus corax) from Ireland, presented by Captain 

 Ogilby ; a Cheetah {Cyncehirus jubatiis) from Persia, three 



Blandford's Rats {Mus blandfordi), two Terrapins 



{Clemmys sp, inc.) from India, deposited ; two Coypus {Myopo- 

 tanius coypus) from South America, two Andaman Starlings 

 {Sturnia andavianensis) from the Andaman Islands, two Red- 

 billed Hornbills {Tocais erythrorhynclms), two African White 

 Spoonbills {Plalaka alba) from Africa, two Virginian Eagle 

 Owls {Bubo virginiarius) from North America, purchased ; a 

 Red V>^Qx{Cervus elaphus i ), a Japanese Deer {Cei-vus sika 9 ), 

 bom in the Gardens. 



OUR ASTRONOMICAL COLUMN. 

 The Meridian Photometer. — In vol. xxiii. of the Annah 

 of the Harvard College Observatory, Prof. E. C. Pickering and 

 O. C, Wendell give and discuss the observations made at Cam- 

 bridge, U,S., with the meridian photometer during the years 

 1882-88. The observations relate principally to stars north of 



NO. TT27, VOL. 44] 



the declination - 40°. Vol. xiv. of the Annals contained the 

 results of observations of the brightness of stars made with a 

 small meridian photometer. The present volume deals with 

 the photometric measurements of somewhat fainter stars, made 

 by means of a similar but larger instrument. 



Report of Harvard College Observatory.— Prof, 

 Pickering has just issued his Report for last year. He agajn 

 urges the necessity of a fire-proof building for storing the 

 27,000 photographic plates of spectra, 9000 of which were 

 taken in 1890. Legacies for the endowment of science in 

 America are so common that it is not surprising to learn that 

 the Observatory has received a gift of 25,000 dollars through the 

 late Mr. J. I. Bowditch. During the past year 1309 photo- 

 graphs of stellar spectra have been taken with the Bache tele- 

 scope at the station near Closica, in Peru. Nearly all of them 

 relate to the region south of - 20°. Mrs. Draper has added 

 another instrument of the same kind to the Henry Draper 

 Memorial. This is mounted in the Observatory grounds at 

 Cambridge, and since September 1889, 2157 photographs 

 have been taken with it, covering the sky north of - 20 . By 

 placing a prism of small angle over the objective, the spectra of 

 stars as faint as the tenth magnitude have been obtained. Six 

 stars with Type IV. spectra have been discovered. Spectra 

 of fifteen planetary nebulae have been photographed. The 

 hydrogen line F has been shown to be bright in eight stars. 

 Bright line stars of the Wolf- Ray et type now number twenty- 

 eight, three having been added to the list during the past year. 

 The names are given of thirty variable stars of long period, ih 

 which the hydrogen lines are bright at maximum. This pecu- 

 liarity has furnished a means of discovering seven new variable 

 stars. The ii-inch telescope has been used for a detailed study 

 of the spectra of the brightest stars, with the result that /3 Aurigae 

 and C Ursse Majoris have been discovered to be close binaries. 

 One photograph of <r Herculis seems to show that this star also 

 is double, but this has not been confirmed. With the 12-inch 

 telescope a number of "canals " on Mars have been recognized, 

 but only one of them was distinctly seen to be double. An im- 

 portant accession to the white spot surrounding the southern 

 pole was found by photographs to have occurred between the 

 nights of April 9 and 10. The Report concludes with a list of 

 the numerous publications issued by the Observatory during the 

 year. 



THE SOLAR PARALLAX AND ITS RELATED 

 CONSTANTS. 



TT would be difficult to conceive a more masterly and compre- 

 hensive exposition of astronomical and physical constants 

 than one just issued by Prof. W. Harkness, of the United States 

 Naval Observatory. As is rightly pointed out, " The solar 

 parallax is not an independent constant. On the contrary, it is 

 entangled with the lunar parallax, the constants of precession 

 and nutation, the parallactic inequality of the moon, the lunar 

 inequality of the earth, the masses of the earth and moon, the 

 ratio of the solar and lunar tides, the constant of aberration, the 

 velocity of light, and the light equation." It should therefore 

 be determined simultaneously with all these quantities by means 

 of a least-square adjustment, and Prof. Harkness develops such 

 a method. The equations connecting the constants are given, 

 whilst the numerical values which are discussed are based upon 

 an enormous mass of astronomical, geodetic, gravitational, and 

 tidal observations which have required more than two hundred 

 years for their accumulation. The sources of probable error are 

 also examined, and it is suggested how some of the constants 

 may be improved in the future. The completeness of the lists 

 of constants, and the careful manner in which they are discussed 

 and corrected by the comprehensive least-square adjustment whicli 

 is developed, justifies our giving seriatim the results obtained : — 

 Equatorial semi-diameter of the earth — 



3963 1 24 ± 0078 miles. 

 Polar semi-diameter of the earth — 



3949-922 ± o"o62 miles. 

 One earth quadrant — 



ioooi8i6± I25'i metres. 

 Oblateness or flattening of the earth — 



1/300 "205 ± 2-964. 

 Eccentricity of the earth — 



o '00665 10 1 8. 



