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NATURE [October i8, 1906 



In Engineering (vol. Ixxxii., No. 2126) an abstract is 

 given of a paper by Mr. A. R. Ledoux, presented to the 

 American Institute of Mining Engineers, describing a new 

 method of mining kaolin. Deposits in the Housatonic 

 River district in Connecticut were being worked at a loss, 

 owing to transport difficulties and to increase in expenses 

 caused by the dip of the vein, which ran at an angle of 

 about 50 degrees from the vertical, between gneiss and 

 hornblende schist, and a footwall of rock. The material 

 is therefore now mined by well, by which method the 

 crude material is obtained with but little of the over- 

 burden, &c. The wells are from 50 feet to 198 feet deep, 

 and contain a 4-inch, and, inside this, a 2-inch pipe. 

 These go down gradually into the clay. Water at a pres- 

 sure of about 40 lb. per square inch is forced through the 

 smaller pipe, and on its passage upward carries with it 

 about 5 per cent, of solid matter, of which 75 per cent, is 

 pure kaolin. 



Much valuable information regarding the mineral re- 

 sources of Peru continues to be got together in the admir- 

 able series of monographs issued by the Government Corps 

 of Mining Engineers. In Boletin \o. 29 Mr. Federico G. 

 Fuchs describes the copper-bearing region in the vicinitv 

 of lea and Nazca. His detailed description, covering loo 

 pages, and his geological map show the importance of a 

 mining centre that has long been neglected. In Boletin 

 No. 35 Mr. Enrique I. Duenas reviews the mineral re- 

 sources of Jauja and Huancayo. At the present time no 

 mines are being worked in these provinces, but the author 

 shows that they are rich in coal, asphalt, copper, silver, 

 gold, molybdenum, and iron. In Boletin No. 36 Mr. Luis 

 Pfliicker describes the iron-ore deposits of Aija and Calley- 

 cancha. The ore, which occurs in veins, is of great purity 

 and richness, but the absence of fuel is, in the case of the 

 Aija deposits, unfavourable to their development. The 

 Calleycancha veins are more promising owing to their 

 proximity to the Mancos coalfield. 



The address delivered by Mr. James .'Vdamson, hon. 

 secretary to the Institute of Marine Engineers, on 

 October i, dealt in a scholarly manner with the advantages 

 of a technical society. To the individual member, the 

 advantages are in the direction of mental exercise, and 

 consequent strengthening of the faculties of the mind ; in 

 the direction of finding out, in the course of discussions 

 with fellow-craftsmen, how troubles in connection with 

 details have been met and difficulties overcome ; in the 

 direction of social intercourse, and in exchanging experi- 

 ences for mutual benefit. The advantages to the com- 

 munity of which the members of the society are units 

 are in tending to improve the conditions of life and work 

 all round ; in tending to bring to the front, for the 

 benefit of all, the latest improvements and developments ; 

 in tending to educate the general public in respect to the 

 various aspects of the world of science, and to give the 

 people a better understanding of things within the domain 

 of science. The advantages to the nation are in tending 

 to improve the trade of the country by improving methods 

 of manufacture ; in tending to improve material and 

 minimise risk of failure ; in tending to lessen insurance 

 premiums by lessening risk of breakages, stoppages, and 

 disablements ; in tending to the adoption of improved 

 methods, material and appliances, with better conditions of 

 upkeep and improved views in respect to upkeep and ex- 

 penditure, to get the best results in immediate running 

 and prospective life average, thus minimising costs and 

 economising capital outlay, with consequent advantages in 

 competing for the traffic of the world ; and in tending to re- 

 NO. 1929, VOL. 74] 



duce the cost of material and running expenses and repairs, 

 enabling employers to lessen the cost of output, and make 

 improvements in their plant to enable them to keep up to 

 date in their works and factories with all competitors. 



During the past few years several theories have been 

 advanced connecting the fluorescence of organic sub- 

 stances with their chemical constitution. A new hypothesis 

 is now suggested by Profs. Luigi Francesconi and G. 

 Bargellini, based on the examination of a very large number 

 of substances by a very sensitive method which they have 

 devised for detecting fluorescence (Atti dei Lincei, series 5, 

 vol. XV., No. 3). When a beam of sunlight is concentrated 

 by a lens on a solution of the substance contained in a 

 test-tube in a darkened box, and the liquid is examined 

 from above, the cone of light appears, in the case of fluor- 

 escent substances, of a different colour from that of the 

 solution. The striking fact has been elicited that aliphatic 

 substances do not show fluorescence, and the same holds 

 true of alicyclic compounds in which fatty groups pre- 

 dominate. It is contended that all aromatic substances are 

 potentially fluorescent, and that a greater or less degree 

 of fluorescence is to be attributed to the presence of certain 

 groups or radicals which enhance or diminish the effect, 

 each group possessing a specific influence. 



The chemical and electrical effects induced by ultra- 

 violet light in the case of certain elements have recently 

 attracted attention, and explanations have been advanced 

 based on the electronic theory of matter. In this connec- 

 tion an investigation of the photoelectric properties of 

 anthracene, by A. Pochettino (Atti dei Lincei, series 5, 

 vol. XV., ii., p. 171), has a special significance. It has 

 long been recognised that anthracene is highly fluorescent, 

 and the author has recently proved that this fluorescence is 

 accompanied by " ionisation " of the air in the neighbour- 

 hood of the anthracene. In the paper cited it is shown that 

 the photoelectric effect of anthracene is very nearly the same 

 as that of zinc, and that, as with zinc, the activity decays 

 with time. This decay is, however, observed only when the 

 layer of anthracene exceeds a certain thickness (002 mm.), 

 and is attributed to the high dielectric properties of the 

 material, which, by allowing the accumulation of a positive 

 charge on the anthracene, arrests the ionisation effect. The 

 original activity of anthracene which has completely lost 

 its photoelectric properties can be restored, not only by 

 leaving the material in darkness, but by exposing it during 

 a few minutes to the radiation of radium, which serves to 

 neutralise the positive charge. The decay of the activity 

 with time is capable of being expressed by an exponential 

 curve. Similar results are noticed in the case of 

 phenanthrene. The resemblance of the phenomena de- 

 scribed to those characteristic of radio-activity again raises 

 the question, suggested by Armstrong and Lowry in 1903, 

 of the relationship of radio-activity and fluorescence. In 

 the case of anthracene, atomic degradation is hardly prob- 

 able ; the fluorescence of anthracene is, indeed, generally 

 attributed to molecular transformation involving the change 

 of one structure into another under the influence of light. 

 Whether radio-activity is not also a molecular, as dis- 

 tinguished from an atomic, change, caused by an externa! 

 stimulus, similar to, if not identical with, light, is a 

 question which naturally arises from the analogy presented 

 by the two cases. 



A.v elaborate work on salt and salt mines is in course 

 of publication by Mr. W. Engelmann, Leipzig, for the 

 Vienna Academy of Sciences, under the title " Das Salz : 

 dessen Vorkommen und \'erwertung in samtlichen Staaten 



