August 21, 1908] 



SCIENCE 



233 



that three of the Australian colonies are 

 scarcely in a position to undertake this new 

 work; but South Australia is freer, and if it 

 can establish a solar observatory, either at 

 Adelaide or elswhere, a gap in longitude will 

 be satisfactorily filled. The scheme is receiving 

 substantial private support. In addition to the 

 promise of a telescope (a 6-in. Grubb equa- 

 torial refractor) from the trustees of the 

 estate of the late Lord Farnham, Dr. W. 

 Geoffrey Duffield, of the Physical Labora- 

 tories, Manchester University, has received 

 from Mr. Frank K. McClean the offer of £500 

 towards the purchase of a large spectrohelio- 

 graph, on condition that an additional sum of 

 £1000 be privately subscribed towards the 

 same piece of apparatus. 



UNIVERSITY AND EDUCATIONAL NEWS 



The University of Toronto is conducting a 

 course in hygiene of twenty lectures. Dean 

 Reeve of the medical faculty will take up the 

 eye and ear; Dr. George R. McDonagh, the 

 nose and throat; Dr. Charles Sheard, con- 

 tagious and infectious diseases; Dr. Abbott, 

 color blindness, and Dr. William Oldright, 

 general sanitation. 



Dr. Chas. C. Adams, of the University of 

 Chicago, has been appointed associate in ani- 

 mal ecology at the University of Illinois. 



In the faculty of engineering at University 

 College, London, a new lectureship in elec- 

 trical design has been instituted, to which Mr. 

 Henry Metcalf Hobart has been appointed. 



Mr. W. Jackson Pope, F.E.S., professor of 

 chemistry in the University of Manchester, 

 has been elected into the professorship of 

 chemistry, at Cambridge, rendered vacant by 

 the resignation of Professor G. D. Liveing, 

 who has held the chair since 1861. Mr. Pope, 

 who was born in London in 1870, was educated 

 at Finsbury Technical College and the Cen- 

 tral Technical College, London. Before go- 

 ing to Manchester he was head of the chem- 

 istry department of the Goldsmiths' Institute, 

 London. 



Dr. Hans Speman, of the University of 

 Wiirzburg, has been appointed professor of 

 zoology at the University of Rostock. 



DISCUSSION AND CORRESPONDENCE 



THE chemical FORMULA OF THE MINER.\L 

 BENITOITE 



In a recent issue of Science (May 1, 1908) 

 Mr. Edward H. Kraus discusses the recently 

 described mineral benitoite, and suggests a 

 formula which differs somewhat from the one 

 proposed by Professor Louderback in his orig- 

 inal paper. The two analyses already reported, 

 and a third which will be published shortly, 

 all show that the empirical formula of the 

 mineral is BaTiSijO,, and the most reasonable 

 assumption is that it is made up of the three 

 oxides BaO, TiO^ and SiO^. Mr. Louder- 

 back's proposal is that the mineral is a very 

 acid titano-silicate of barium, whereas Mr. 

 Kraus suggests that the titanium here plays 

 the part of a base and that therefore the min- 

 eral is a double metasilicate of barium and 

 titanium. Though it must be admitted that 

 absolute proof of the correctness of either of 

 these two suggestions is at present scarcely 

 possible it seems to me that the arguments 

 advanced by Mr. Kraus are entirely unsatis- 

 factoiy and I submit the following objections. 



The main argument upon which Mr. Kraus 

 bases his formula is the alleged isomorphism 

 of benitoite with beryl, which mineral is usu- 

 ally regarded as a salt of metasilicic acid. 

 If the most favorable values are chosen the 

 ratios of the a axis to the c axis for the two 

 minerals are 1.4989 and 1.4230, respectively. 

 These figures show an actual difference of 

 more than sixteen per cent, of the magnitude 

 concerned, and even interpreting the law of 

 isomorphism with that degree of looseness 

 which is not uncommon among mineralogists, 

 furnish no evidence upon which to base con- 

 clusions as to the molecular structure of the 

 two compounds. The two minerals also differ 

 widely as to form and habit; one is trigonal 

 and the other holohedral. Further, many of 

 the illustrations which Mr. Kraus cites as 

 examples of isomorphism are open to serious 

 question; galena and argentite most certainly 

 can not be called isomorphous merely because 

 they both crystallize in cubes. 



The occurrence of benitoite in rock forma- 

 tions which are of a basic character, upon 



