142 



SCIENCE. 



[Vol. XIII. No. 316 



SCIENCE 



A WEEKLY NEWSPAPER OF ALL THE ARTS AND SCIENCES. 



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NEW YORK, Feb. 22, iS 



No. 316. 



CONTENTS: 



Practical Electric-Railway Pro- 

 pulsion 133 



The WoRTHiNGTON Independent 

 Condenser I34 



The Development of the Pot- 

 terv Industry of the United 

 States 136 



Health Matters. 



Yellow-Fever T36 



Legal Regulation of Medical Prac- 

 tice 136 



Contagiousness of Consumption 137 



Doctors Advertising 137 



Public Medical Libraries 137 



Danger in the Postage-Stamp r37 



Sanitary Plumbing 137 



Electrical News. 



Hertz's Researches on Electric Os- 

 cillations 137 



Electricity and Light 138 



Light Motors for Aeronautic Experi- 



139 



Important Patent Decision . . 



Notes and News 139 



Editorial 142 



United States at the Paris Exhibition. 



Photographic Map of 1 

 MAL Solar Spectrum. 



NoR- 



23 



Earthquake of Liguria, Feb. 

 OF Ph 



Nature and Oi 

 OF Lime. . . . 



Social Progress ' 



Scientific Religion 



German Commercial Correspo 



French Commercial Correspondence ; 

 i of Plane Analytic Geome- 



try. 



The Beginner's Reading Book i 



Among the Publishers i 



Letters to the Editor. 



O'Reilly's "Greenland" 



yo7iK Murdoch 1 

 The Soaring of Birds 



W.H.Pickering: y.G.MacGregor 1 

 Some Habits of the Omahas 



J. Owen Dorsey ] 

 Sawdust Explosion Robert Bell i 



The United States will make a creditable display at the 

 Paris Exhibition. And this is as it should be ; for, although nom- 

 inally a universal exposition, it will be practically a display of the 

 products of republics. The monarchies of Europe will be repre- 

 sented only by private exhibits, while the republics of North and 

 South America have rallied in force. The United States Depart- 

 ment of Agriculture will make a splendid showing. Secretary 

 Colman has placed the undertaking in the hands of Professor C- 

 V. Riley, the famous entomologist, an energetic organizer as well 

 as a careful and enterprising scientific observer ; and Professor 

 Riley has already sent forward three car-loads of products, which 

 are on the way to France in charge of Mr. F. T. Bickford, an as- 

 sistant. The bulk of shipments are nearly through with, and the 

 perishable staples will follow during the next month. Congress 

 appropriated $250,000 to aid exhibiters, and Secretary Colman's^ 

 quota of this will insure the best illustration that the agricultura. 

 resources of this country have ever had on the continent of Europe 

 Various branches will be represented as follows : fruit. Professor 

 VanDeman and Professor George Hussman ; grain, George N. 

 Hill, St. Paul, Minn. ; cotton and fibres. Col. James A. Benford, 

 Duck Hill, Miss., and Charles R. Dodge, Boston ; tobacco and 

 peanuts, Alexander McDonald, Va. ; agricultural education and 



experimental stations, W. O. Atwater, Department of Agriculture ; 

 vegetables, including hops, M. G. Kern, St. Louis ; entomology, in- 

 cluding apiculture and silk-culture, C. V. Riley, N. W. McLean of 

 Hinsdale, 111., and Philip Walker, Department of Agriculture ; sor- 

 ghum and other sugar-plants, H. W. Wiley, Department of Agri- 

 culture ; forestry, B. Fernow, Department of Agriculture, and M. 

 G. Kern of St. Louis ; grasses and forage-plants, George Vasey, 

 Department of Agriculture ; meat products, Dr. de Salmon, De- 

 partment of Agriculture. All articles for exhibition will be for- 

 warded free from New York, and no charge will be made for space 

 in Paris. Professor Riley has put forth unusual exertions to get 

 the exhibit on the road, and he looks forward with much enthusi- 

 asm to the result. He will not leave for Paris till the first week in 

 April. 



PHOTOGRAPHIC MAP OF THE NORMAL SOLAR 

 SPECTRUM. 



A new and greatly improved edition of this map, made by Pro- 

 fessor H. A. Rowland, extending from the extreme ultra violet 

 down to and including B to wave-length 6950, is now ready. The 

 old map, published in 18S6, was made by means of a grating ruled 

 on the old dividing-engine, which was originally intended for only 

 small gratings, and at a time when Professor Rowland's knowledge 

 of photography was limited. Furthermore, it was not printed in a 

 sufficiently careful manner ; and the negatives, which were origi- 

 nally none too good, soon became broken or defaced, so that many 

 of the prints, especially the later ones, were not satisfactory. 



The whole work has now been gone over again. A new dividing- 

 engine to rule large gratings has been constructed, and has proved 

 to be superior in every way to the old one, although the old one is 

 almost equal to it for small-size gratings. It has been placed in 

 the vault of the new physical laboratory, where an almost constant 

 temperature is maintained. Several concave gratings of 6 inches 

 diameter and 21+ feet radius have been ruled with 10,000 or 20,000 

 lines to the inch, giving definition hitherto undreamed of. These 

 have been mounted in the best possible manner. The laboratory 

 contains rooms for developing, making emulsions and dry plates, 

 complete enlarging apparatus, and, indeed, every facility for photo- 

 graphic work on the spectrum of the sun ; and a large steam-engine, 

 a variety of dynamos, continuous and alternating current, with 

 Ruhmkorff coils of all kinds, one of which latter will melt down iron 

 wire larger than one-sixteenth of an inch in diameter in the second- 

 ary circuit, give means of future investigation on the spectrum of 

 the elements. Professor Rowland has devoted years to the making 

 of dry plates, simple and orthochromatic, and is thus better pre- 

 pared than before for the work of making the map. He has also re- 

 vised his list of standard wave-lengths, and extended them into the 

 ultra violet, and has placed the scale upon the photographs with 

 greater care than before. The printing is carried on in Baltimore, 

 where it is under the immediate supervision of Professor Rowland. 



The negatives have been made on thick French plate glass, and 

 the prints are much more artistic than the old ones. The definition 

 is not only much finer throughout, but the prints are much more 

 uniform, and have fewer spots. 



The process of making this map is the same as that used for the 

 old one, and is based on the property of the concave grating as 

 discovered by Professor Rowland : this property is, that the spec- 

 trum, as photographed in any given order, is normal, and of the 

 same scale throughout. The focus remains automatically adjusted, 

 so that one has only to move the instrument to the part of the spec- 

 trum required, absorb the overlying spectra, and put in the photo- 

 graphic plate. The negatives enlarged have been selected from 

 many hundreds taken from different gratings, though three gratings 

 were finally selected for the work. The negatives from any given 

 order of spectrum are measured from one standard line to another 

 on a dividing-engine, so that the constant of the dividing-engine is 

 known. The scale is then made by ruling on a piece of French 

 plate glass having a coating of blackened collodio-chloride. The 

 negatives are then clamped to the scale firmly, after being adjusted 

 into position by the standards. They are then put in the enlarging 

 apparatus, and the whole enlarged from two and a half to possibly 



