September 2, 1915] 



NATURE 



17 



a mutual influence of closely neig^hbourinjif Fraun- 

 hofer lines. Early in the present year, however, Dr. 

 St. John, discussing the same data employed by 

 Julius, obtained a ne^^ative result. The matter is 

 now carried a stage further in the June number of 

 the Astrophysical Journal by Mr. Sebastian Albrecht. 

 In this valuable paper a comparison is made of Row- 

 land's solar wave-lengths of iron lines and the labora- 

 tory wave-lengths of the same lines to determine 

 whether systematic difTerences are shown by lines 

 having close companion and isolated lines. The paper 

 hinges on a discussion of laboratory wave-lengths. 

 All iron lines which have been classified according to 

 pressure effect were examined, and consequently a 

 chief feature of the paper is a complete list of Row- 

 land's solar wave-lengths and corresponding inter- 

 national wave-lengths of these lines. International 

 secondary standards were, of course, adopted without 

 modification ; for other lines a comparison was made 

 between the sea-level determinations of Burns and 

 the Pasadena-Mount Wilson values of St. John and 

 Ware. A systematic difference so disclosed was 

 ascribed to differences in the internal pressure of the 

 arcs employed. The corrections to reduce the I. A. 

 values to a pressure of 05 atm. (the pressure of the 

 solar reversing layer) were applied, and differences, 

 Row., A I. A. 05 atm., as well as Row. A I. A. 

 I atm., were tabulated. Systematic differences 

 between Rowland and the international system were 

 eliminated subsequently by means of a curve. The 

 following table concisely exhibits the principal results 

 obtained : — 



Means — Displacement according to Separation of 

 Lines. 



Separation 

 Lines with ^ — ^ ^ ^ 



o-o to 0-2 A 0-2 to 0-4 °''* *"'* 



. greater 



Companion towards red ... -fo-oio3 ... -(-o"oo6s ... -f 0*0036 



., ,, blue... -0-0073 ••• -0-0024 •• -o-ooio 



A Remarkable Group of Solar Spots.— The solar 

 surface has recently displayed considerable activity, 

 and possessors of telescopes have been much interested 

 in the number and variety of spot groups almost con- 

 tinually visible. One large group which appeared 

 during three, and possibly four, rotations forms the 

 subject of an article by M. Camille Flammarion in 

 the July number of L' Astronomic . An account is 

 given of the solar activity during the spring months, 

 and associated terrestrial, magnetical, and electrical 

 disturbances. 



A Catalogue of Star Clusters.— The star clusters 

 shown on the Franklin-Adams chart plates have been 

 catalogued by Mr. P. J. Melotte (Mem. Roy. Ast. 

 Soc, vol Ix., part 5). The scale of the plates has 

 been found excellently well adapted for the purpose, 

 the open clusters not being dispersed by excessive 

 magnification, whilst the scale is sufficient to show 

 ^'le features of globular clusters down to 3' diameter. 

 K' catalogue contains 245 entries, and in addition 

 the usual co-ordinates (iQoo), galactic longitudes 

 and latitudes of the various objects are also tabulated. 

 I The clusters have been classified according to degree 

 of condensation in the following scheme of four 

 ' isses : — (i) Globular clusters, condensed at centre; 

 loose clusters having regular well-defined outline; 

 („S) loose clusters of irregular outline; (4) coarse 

 I clusters. By plotting with reference to Milky Way 

 [ and classification it was found that practicallv' all lie 

 within ±30° of the galactic plane, whilst the globular 

 1 lusters also tend to concentrate in a particular longi- 

 tude rather more than half lying within 30^^ of galactic 

 [longitude 325°. 

 NO. 2392, VOL. 96] 



INDIGO IN INDIA. 



THAT the production of natural indigo in India is 

 at present receiving the scientific attention which 

 is its due must be welcome to many. The evidence 

 that this is the case will be found in a Report on 

 the Improvement of Indigo in Bihar, with Notes on 

 Drainage and on Green-Manuring, by Mr. A. 

 Howard, Imperial Economic Botanist at Pusa, and 

 Mrs. Howard, published in 19 14 by the Bihar 

 Planters' Association, and republished this year, with 

 a second report by the same authors, on behalf of 

 the Pusa Agricultural Research Institute. 



The old belief that the source of the natural indigo 

 of commerce is the species of Indigofera distinguished 

 as /. tinctoria, though accepted by many chemists 

 and some botanists in Europe down to the close of 

 last century, was singularly incorrect. That the 

 species in question does yield indigo is true ; that at 

 one time it was a main source of the dye is possible. 

 It is, however, improbable that any appreciable 

 amount of commercial indigo has been derived from 

 /. tinctoria during the past hundred years. 



When the intercourse between Europe and India 

 which followed the discovery of the Cape route began, 

 there were two main centres of indigo production 

 and export. One of these was Surat, in Western 

 India, where the plant employed was a form of 

 Egyptian indigo, /. articulata, still the staple indigo 

 plant in Eritrea, and still to be met with as a native 

 crop in parts of Scinde, Rajputana, and the Deccan. 

 The other was in Southern India, especially in Coro- 

 mandel, and in Ceylon. The plant grown in this area 

 differed much from Egyptian indigo. We may speak 

 of it as Indian indigo, though with some reserve, 

 because a plant from which indigo is obtained in 

 Northern Nigeria cannot be distinguished from the 

 Coromandel one, while a form closely related to it, 

 which is wild in Nubia and the Eastern Sudan, has 

 by some writers been believed to belong to this 

 species. It is not inconceivable that the cultivated 

 plant of Southern India may, like that of Scinde, 

 have originally found its way east from Africa, and 

 it is possible to imagine that on its way west from its 

 original Nubian home to Nigeria, cultivation may 

 have induced in it the same modifications as have 

 taken place on its way east to Madras. The point 

 which immediately interests us, however, is the fact 

 that the name /. tinctoria, as originally employed, 

 connotes the cultivated indigo of Coromandel. 



European needs induced an extension of indigo 

 cultivation. That of the Egyptian plant spread east 

 from Scinde to the Panjab, and thence along the 

 Gangetic Plain to the province of Bihar, in later 

 times so closely associated with the manufacture of 

 indigo. The cultivation of the Indian indigo spread 

 to Malaya in the east, to the coasts of Madagascar, 

 Zanzibar, and Socotra in the west; somehow, this 

 indigo has even reached Northern Queensland. But 

 neither plant extended to Bengal, or to Indo-China 

 and China beyond Bengal. In Malaya the cultiva- 

 tion of Indian indigo went on along with that of a 

 third plant, /. stnnatrana, which we may speak of a& 

 Malayan indigo; this plant has found its way east- 

 ward to Formosa and, during the supremacy of the 

 Dutch in Western India, was brought from Sumatra 

 to Malabar, where it displaced both Indian indigcv 

 and yet another dye-yielding Indigofera. This fourth 

 plant, I. longeracemosa, hardly deserves a com- 

 mercial name, and only calls for mention because it 

 has found its way to the Mascarenes and Zanzibar, 

 and is preferred there to the other dye-yielding species. 



This is not the jilace to discuss the policy which, 

 early in the seventeenth century, laid an embargo on 



