¥ 



SCIENCE 



Sixth Year. 

 Vol. XII. No. 288. 



NEW YORK, August io, il 



Single Copies, Ten Cents. 

 I3.50 Per Year, in Advance. 



Entered at New York PoBt-Offloe as Seoond-OlasB Mail-Matter. 



Sketch-Map of the United States. (' ..^/,^^^\ 



Editorial ...... 



The Captives of the Mahdi. — The Prompt Issue of the Geo- 

 logic.ll Survey Publications. — The Redemption of the Arid 

 Region l)y Irrigation. 



The Census Maps of the United States 



Dr. F. Boas . 

 James Stevenson ..... 

 Scientific News in Washington. 



Oil-Exploding Rockets ..... 



How a Mound was built . 



The Pilot Chan of the North Atlantic Ocean 



Electrical Science. 



61 



61 



63 



64 

 65 

 65 



Change of Potenti.il in a Voltaic Couple by Variation of Strength 



of the Liquid . . . . . .66 



The ' Minimum Point ' of Change of Potential of a Voltaic 



Couple . . . . . .66 



Electrical Tr.-atment of Zinc and its Ores . . .66 



Electric Te^tint; Bureau at Johns Hopkins University . 67 



v^ AUG 13^ 



Health Matters. 



Malaria . 



Cancer . 



Typhoid Fever 



A Simple Filler . 



Precautions in Bathing 



The Tuning-Fork in the Diagnosis of Ear Affections 



Book-Reviews. 



Ptomaines and Leucomaines .... 



Longmans' School Geography .... 



Elementary Physiography ..... 



Notes and News ..... 

 Letters to the Editor. 



Our Native Birds BmJford Torrey ; Frank M. Chapman 



The Relation between the Sourness of Certain Acid Solutions 

 and the Amount of Acid contained . E. H. S. Bailey 



Beware of the Deadly Alternating Electric Current 



Dr. Cyrus Edson et al. 

 Note on Breeding-Habits of the Bill-Fish Charles C. Abbott 



<n 



67 

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 63 

 68 

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69 

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The Science Company, Pitblishers, 47 Lafayette Place, New York. 



London agrcnt : G. E. Stechert, 26 Kin^ William St., Strand. 



THE GREAT Gs^dwri ;"'"'"'' -K 



ROUTE. 



Hew York Central and Huosbn River Hailroai 



THE ROUTE OF THE "FAST MAIL" AND THE FAMOUS VESTIBULED 

 "NEW YORK, CHICAGO, AND ST. LOUIS LIMITED." 



Two of the four tracks are devoted exclusively to Passenger Trains. This in connection with the easy grades. 

 liclir riin/cs and sunerior construction, makes the New York Central and Hudson River Railroad THE SAFEST, 

 q'iJICkTsT AND MOST C^^^^ ROUTE BEfWEEN NEW YORK OR BOSTON AND 

 THE WEST. 



The Niagara Falls Route 

 V,.rk Central & Hudson River R.lil: 

 ncction with the Michigan Central Railroad. crosS' 

 in.T Niagara River on the celebrated Cantilcvei 

 I'.ridge within a few hundred yards of ihe falls 

 All trains stop ten minutes at Falls y 

 ,(t the verge of the .great cataract and 

 ..I the rapids just atove the falls. 



All Trains arrive at and depart from the Gri 

 ;entral Station, New York ; the largest and fin 

 Railway Staiion in America, and the only Tn 

 :,ine station in the city of New York. 



M AGNIFIC 



New Wag 

 Sleeping Cars. 



Run regularly to and from New York and Boston and make direct connection to and from 



BUFFALO, CLEVELAND, ST. PAUL, TEXAS, 



NIAGARA FALLS, CINCINNATI, MANITOBA, DENVER, 



TORONTO, INDIANAPOLIS, PORTLAND, SALT LAKE. 



DETROIT, St. LOUIS, KANSAS CITY, SAN FRANCISCO, etc. 



For Time Tables or information call on nearest Ticket Agent of the Boston .ind .Mb: 

 New York Central, Lake Shore and Michigan Southern, or address 



JIf. C. ItOACH, HENBT MONETT, 



Gent Eastern Passenger Agent, Gen I Passenger Agent, 



No. 413 Broadway, New York City. Grand Central StoUon. THE WORLD-FAMED HUDSON RIVER. 



C^" Delegates to the Meeting of the General Association for the .Advancement of Science should avail tliemselves of the reduced rales 

 the New York Centr.al, and travel over the Great Four Track Route. 



offered by 



