320 



NATURE 



[February i, 1894 



portant diamond mine in South Africa is that of Jagers- 

 fontein, situated in the Orange Free State, about eighty 

 miles to the south-east of Kimberley. 



The diamond mines of South Africa are not less 

 remarkable for the size of the individual stones 

 that they have yielded, than for the vast amount 

 of the precious material with which tiiey have 

 flooded the markets of the world. The "Braganza" 

 diamond, which belonged to the Emperor of Brazil, 

 is said to weigh 1680 carats, but it has never been 

 subjected to the inspection of experts, and there is every 

 reason to believe that it is nothing but a colourless topaz. 

 In the same way the reputed diamond of the Rajah of 

 Matan in Borneo (367 carats) has been recently 

 shown to be only a piece of quartz. The " Great 

 Mogul," the Regent or Pitt diamond, and the Koh-i-nur, 

 the finest productions of the Indian mines, are said to 

 have originally weighed 787I, 410, and 193 carats re- 

 spectively, but were reduced by cutting to 279/,.;, 136^-, 

 and \02\ carats. The Brazilian mines have yielded the 

 Portuguese Regent and the Star of the South, the former 

 of which, on cutting, yielding a gem of 215 carats, while 

 the latter weighed 254^ carats in the rough. 



The South African 'mines have, however, produced 

 stones surpassing in size all those hitherto obtained either 

 from India or Brazil. Some of these stones are, it is 

 true, of a yellow colour, and therefore of comparatively 

 small value ; but others, like the Porter- Rhodes diamond 

 (150 carats), the De Beers diamond (428A carats), and 

 the Jagersfontein diamond (969^ carats) — the last-men- 

 tioned having been discovered as recently as June 30, 

 1893 — are remarkable for their freedom from any trace \ 

 of yellow tint, and for the perfect whiteness or even 

 blue-whiteness of their colour. We are able to give 

 outlines drawn to the true scale of the two largest South ', 

 African diamonds, the one characterised by its crystalline ' 

 form (a regular octahedron), the other by its irregularity 

 of shape. These are taken from Mr. Reunert's book. 



Another book on precious stones that has recently 

 appeared is of a very different character, and deals not 

 only with the diamond, but with all the other materials 

 held in esteem ^by jewellers.^ The two works are, how- 

 ever, equally entitled to praise for the accuracy and 

 fulness of the information they supply, and for the manner 

 in which the latest sources of information have been 

 utilised. 



The distinguishing feature of Dr. Doelter's book upon 

 precious and ornamental stones is the care which has 

 been bestowed upon the directions for their easy and 

 certain discrimination. In the earlier chapters, the 

 descriptions of the various methods for determining and 

 accurately defining the specific gravity, cleavage, hard- 

 ness, refractive index and double refraction, as well as 

 the colour, pleochroism, and absorption of minerals, are 

 very full and entirely satisfactory. The second part of 

 the work contains systematic descriptions of the minerals 

 employed for purposes of ornament ; and these, as might 

 be expected from a mineralogist of Dr. Doelter's position, 

 leave nothing to be desired in the way of completeness 

 and accuracy. No less admirable are the accounts given 

 of the artificial production of these minerals, of the 

 materials made to imitate them, and of the value of gems 

 and the modes of cutting them. Details of this kind are of 

 much practical v^alue, and add greatly to the usefulness of 

 the book as a work of reference. The position of certain 

 minerals in the estimation of jewellers is liable to vari- 

 ation as the popular taste changes, and it is certainly 

 not the same in different countries. Dr. Doelter's classi- 

 fication will, however, we think be generally accepted as 

 a judicious one. Of precious stones proper he admits 



1 " Edelsteinkunde ; Bestimmung und Unterscheldung der Edelsteine und 

 Schmucksteine. Die Kiinustliche Darstellung der Edelsteine. " Voq Dr.C. 

 J)oeker, o " Prof, der Mineralogie an der K.K. Univer^itat Graz. (Leipzig : 

 V^eit and Co., 1393.) 



NO. T 266, VOL. 49] 



three classes, in the highest of which he places only the 

 diamond, the various forms of corundum, the emerald, 

 and the spinel, though possible exception may be taken 

 to the high position allowed to the last of these. The 

 second-class contains euclase, chrysoberyll, zircon, 

 phenacite, topaz, the noble opal, garnet and tourmaline. 

 To the third class are relegated the turquoise, olivine, 

 cordierite, kyanite, andalusite, staurolite, hiddenite, 

 axinite, vesuvian, and diopside. The " semi-noble 

 stones" fall into two classes, in the higher of which are 

 placed quartz, chalcedony, agate, felspars, lapis lazuli, 

 and rhodonite, while the lower contains amber, fluor- 

 spar, nephrite, agalmatolite, malachite, and serpentine. 

 It is doubtful whether some of the forms of quartz, like 

 amethyst and cat's-eye, are not deserving of a place 

 among the noble stones proper. 



The third part of the work contains a series of tables 

 for the determination of the minerals which are employed 

 as precious stones. These tables have been drawn up 

 with great care, and cannot fail to prove of very great 

 service to those studying gems and similar materials, 

 either from the scientific or the commercial point of view. 

 The table showing the trade names, and the scientific 

 designations of the several gems, is very complete ; and the 

 whole work may be commended for its union of scientific 

 accuracy with practical usefulness. 



NOTES. 

 The International Sanitary Conference, which was to have 

 opened at Paris on January 24, has been postponed to February 

 7. We learn that President Cleveland has appointed Dr. 

 Edward S. Shakespeare, of Philadelphia, Dr. Stephen Smith, 

 of New York, and Dr. Preston H. Bailhache, of the United 

 States Marine Hospital Service, delegates to represent the 

 United States at the Congress. 



A SLIGHT earthquake visited North Devon about 9 a.m. on 

 Tuesday, January 23. The shock seems to have been felt over 

 the whole of Exmoor as far as South Molton. 



We regret to note the death of Prof. A. Hirsch ; he died 

 at Berlin on January 28, at the age of seventy-six. We have 

 also to announce the death of Dr. G. Adler, Professor of 

 Mathematical Physics in Vienna University. 



Dr. K. von Zittel, Professor of Geology in Munich Uni- 

 versity, has been made a member of the German Privy Council. 



At a public meeting held at Shrewsbury on Tuesday, it was 

 resolved to raise a memorial to Charles Darwin, who was a 

 native of that town. Another public meeting will be held to 

 consider the best method of carrying out the proposal. The 

 Mayor of Shrewsbury, in commenting upon the proposal, rightly 

 remarked that in doing honour to one who had shed an im- 

 perishable lustre on his native town they were doing honour to 

 themselves. In addition to the suggestion that a bronze statue 

 of Darwin should be erected in front of the old Grammar School, 

 now the public library and museum, it was proposed to found a 

 scholarship to his memory in connection with Shrewsbury 

 School. Another suggestion was that the memorial should take 

 the form of a hall of science to be erected in Shrewsbury for the 

 purposes of scientific and technical instruction. 



It is reported that a sum approaching ^^50,000 has been be- 

 queathed by the late Mr. T. H. Adam, of Newport, for the 

 purposes of technical instruction. The money is to be devoted 

 to teaching practical and theoretical agriculture to men and 

 youths, and a knowledge of dairying, housekeeping, and other 

 subjects to women and girls, either by means of lectures or the 

 establishment of a school or schools of agriculture at Edgmond 

 or Woodseaves, in Shropshire, or Chadwell, in Staffordshire, or 

 elsewhere ; or by such other means as the trustees shall think fit. 



