July 12, 191 7] 



NATURE 



JVO 



An interesting addition to the history of the inven- 

 tion of the achromatic telescope is made by Mr. R. B. 

 Prosser in an article in the June number of Notes and 

 Queries. Although in 1758 John Dollond was awarded 

 the Copley medal of the Royal Society for the invention 

 of the achromatic telescope, and is still called the 

 inventor of the instrument in the 1912 edition of the 

 Records of the Royal Society, it has been known for 

 some time that the crown-flint objective had been in- 

 vented previously by Chester Moor Hall, a barrister, of 

 Essex, and the relative f>ositions of Dollond and Hall 

 are set forth by Miss A. M. Clerke in her biographies 

 of the two in the "Dictionary- of National Biography," 

 and by Mr. H. D. Taylor in his article on the telescope 

 in the "Encyclopaedia Britannica. " The new facts 

 brought forward by Mr. Prosser are contained in a 

 I>etition of 1764, from thirty-five opticians of London 

 and Westminster, praying for the revocation of the 

 patent granted to John Dollond for achromatic lenses, 

 on the ground that such lenses were made by George 

 Bast, optician, of Fleet Ditch, to the specification of 

 Hall in 1733, that they were on sale by Ayscough, 

 optician, in Ludgate Hill, and that Robert Raw, 

 optician, of Coldbath Fields, told Dollond of them in 

 1755. This petition was apparently unsuccessful, for 

 in 1766, after the death of John Dollond, his son Peter 

 obtained a verdict against James Champneys, optician, 

 of Cornhill, for infringement of his father's patent, 

 and was awarded 204Z. damages, the judge, Lord 

 Camden, holding that Hall had not adequately "pub- 

 lished " his invention. 



A JOINT meeting of the Faraday Society and the 

 Society of Glass lechnology was held in the Depart- 

 ment of Applied Science at the University of Shetfield 

 on June 20, under the chairmanship of Mr. W. F. 

 Wood. The Vice-Chancellor of the University, Dr. W. 

 Ripper, opened the proceedings with a few words of 

 welcome. The first paper was contributed by Prof. 

 Fearnsides on "The Resources of Refractory Mate- 

 rials Available for Glass Manufacture." Refractories 

 are to be found in different geological formations, but 

 it is noteworthy that many ot the most used substances 

 are in the vicinity of Coal Measures. The occurrence 

 and relative importance of various ganister and fire- 

 clay beds were discussed, and their positions indicated 

 on a large-scale map. The resources of refractories in 

 the West Riding of Yorkshire received particular men- 

 tion, special emphasis being laid on the silica from 

 Meltham, near Huddersfield, ganister from the neigh- 

 bourhood of Sheffield, and fireclay from the Halifax 

 district. Mr. Davidson, of the Glass Technology De- 

 partment of the University of Sheffield, followed with 

 a paper on analyses of clays and their plasticity. He 

 also dealt with the contraction due to drying and 

 firing. Most clays contract between 5 and 6 per cent, 

 in drying. Firing was done at 1000° C., when a linear 

 contraction of from 0-5 to i per cent, was noted, and 

 afterwards at 1450° C., when the contraction varied 

 from 875 to 1 1 per cent, in the majority of cases. Dr. 

 Rosenhain spoke on the desiderata of a good refraok- 

 ton.-, and Dr. Boswell on tlie need of further investiga- 

 tion of the behaviour of pot clays, in which he hoped 

 the glass manufacturers would take part. Mr. Spiers, 

 the secretary- of the Faraday Society, appealed to glass 

 manufacturers to make known their difficulties regard- 

 ing refractories. The main object of the Faraday 

 Society was to concentrate on these difficulties, and up 

 to the present considerable success had been achieved. 



A CONCRETE dam of considerable magnitude — the 

 loftiest, in fact, in the world — has recently been con- 

 structed near Boise. Idaho, U.S.A. Engineering of 

 June 29 gives the following particulars of the work. 

 The dam, which is known as the Arrowrock Dam, is 



NO. 2489, VOL. 99] 



348J ft. high (98 ft. higher than the celebrated Flat- 

 iron Building in New York City), 140 ft. thick at the 

 bottom, and 1100 ft. long at the crest. It cost 

 5,000,000 dollars to construct, and forms part of a 

 scheme involving an outlay of 12,000,000 dollars. In 

 the execution of the work, 683,000 cu. yds. of spoil 

 were removed, and 610,000 cu. yds. of concrete de- 

 posited, with 1,350,000 lb. of steel reinforcement and 

 iSoo tons of structural steel. The object of the dam 

 is to fwovide a store of water for irrigation purposes 

 to serve an area of some 240,000 acres. The reservoirs 

 will accommodate 240,000 acre-feet, and will be fed 

 from the surplus flow of the Boise River, in the late 

 winter and the early spring, when the river is in 

 torrent. An interesting feature of the work is the 

 means provided for dealing with 3,000,000,000 cu. ft. 

 of merchantable timber, located in the basin of the 

 river above the dam, for which the river forms the 

 only practicable exit. A cable lift is installed for 

 handling the logs and depositing them on a concrete 

 deck at the top of the dam, whence they are trans- 

 ferred by spiked rolls to a chain, which conveys them 

 to a gravit}- shoot, where they slide down into the 

 river below. It is stated that the dam has already 

 amply justified its existence by saving the crops on 

 100,000 acres, and that this economy alone would be 

 almost sufficient to defray the total cost of the work. 



In a paper on " Some Compounds of Boron, Oxygen, 

 and Hydrogen" (published by Messrs. H. K. Lewis 

 and Co.) Dr. Travers, with >iessrs. N. M. Gupta and 

 R. C. Ray, describes a :jeries of compounds prepared 

 by the action of water and of ammonia on magnesium 

 boride, BjMgj. These compounds, examined mainly in 

 aqueous solution, include a dioxide, B,0;, an oxide, 

 BiOj, and a sub-oxide, possibly B;0, as well as a series 

 of borohydrates, B^(H,0)„, analogous with the carbo- 

 hvdrates. 



OUR ASTRONOMICAL COLUMN. 



The Nebul-^ .\nd Stellar Evolution. — A full re- 

 port of Prof. W. W. Campbell's address as retiring 

 president of the American Association for the Ad- 

 vancement ,of Science is given in Science (vol. xlv.. 

 No. 1 169). The subject chosen was "The Nebulae," 

 and, besides giving an interesting account of the 

 development of our knowledge of these objects, with 

 an abundance of fine illustrations. Prof. Campbell 

 clearly stated his views as to the place of the nebulae 

 in the cosmical scheme. As to the spiral nebulae. 

 Prof. Campbell considers the hypothesis that they 

 are independent stellar systems, or "external uni- 

 verses," to be in best harmony with the known facts. 

 As regards the gaseous nebulae, while a strong case 

 can be made out for the evolution of planetary nebulae 

 into stars, it cannot safely be concluded that all stars 

 have been developed from nebulae of this class ; their 

 comparative scarcity- and their relatively high veloci- 

 ties are decidedly against such a conclusion. A much 

 stronger case can be made out for the hypothesis that 

 the stars in general have evolved from irregular nebulae, 

 which have spectra identical with those of the planet- 

 aries. These nebulae are closely related spectro- 

 scopically to the bright-line stars, and these again to 

 the early class B stars, and from thence the sequence 

 can be traced through the Sirian and solar types to 

 tlie red stars. This is regarded by Prof. Campbf'l 

 as the most proibable course of stellar evolution. 

 Facts as to the distribution of nebulae and of the 

 different classes of stars seem to him to be opposed 

 to the view that some of the red stars may be at an 

 early stage of evolution. 



