January io, 1890.] 



SCIENCE. 



The New Disk Clutch. 



Among the many interesting devices shown at the recent 

 marine exhibition in Boston was a novel and ingenious disk clutch, 

 the invention of Mr. Walter Hart of this city. This device is in- 

 tended primarily as a safety boat-lowering apparatus, though it is 

 ■equally efficient for hoisting boats or merchandise, by either manual, 

 steam, or electric power. The apparatus consists of a pedestal, to 

 be fastened to the deck or elsewhere, which supports two disk- 



clutches, one at each end of a horizontal shaft. The ropes or falls 

 by which the boat or other article is suspended are placed in these 

 disks, by which they are clutched in such a way as to prevent slip- 

 ping. The motion of these disks is controlled by a hand-wheel, 

 by which the speed of revolution of the shaft and consequent 

 lowering or hoisting of the boat is governed. The machine is 

 compact and powerful, and attracted much favorable attention 

 among men interested in nautical affairs. 



Exchanges. 



and Stereoscopic views of Aborigines of 

 d fine landscapes,etc.,wanted in exchange 

 id fossils. — L. L. Lewis, Copenhagen, 



l^Free of charge to all, if of satisfactory character. 

 Address N. D. C. Hodges, 47 Lafayette Place, New 



York.l 



A few duplicates of Murex radix^ M. rafnosus, M. 

 ■bratjdanst Cassis ru/a, Harfia ventricosa, Oliva tri- 

 atula, O. reticularis^ Chlorostonia funebrale^ Cypraa 

 caput serpentisy C. lynx^ Loitia gigantea., Acinoia. 

 ^atiiia^ Chama sptnosa^ and some thirty other species, 

 for exchange for shells not in our collection. List on ap- 

 plication. — Curator Museum, Polytechnic Society, Lou- 

 isville, Ky. 



Photographs 

 any country', ai 

 for minerals j 

 New York. 



Droysen's Alg^meiner Historicher Hand-atlas (la^y^- 

 2ig, 1886,) for scientific books — those published in the 

 Interfiaiional Scientific Se7-ies preferred.— James H. 

 .Stoller, Schenectady, N.Y. 



Astronomical works and reports wanted in exchange or 

 -to buy. Reports of observations on the planet Neptune 

 -and its satellite specially desired. — Edmund J. Sheri- 

 dan, B.A., 295 Adelphi St., Brooklyn, N.Y. 



I would like to correspond with any person having 

 Tryon's " Structural and Systematic Conchology " to 

 •dispose of. I wish also to obtain State or U.S. Reports 

 on Geology. Conchology, and Archaeology. I will ex- 

 change classified specimens or p;iy cash. Also wanted a 

 copy of MacFarlane's " Geologists' Traveling Hand-Book 

 .and Geological Railway Guide." — D. E. Willard, Cura- 

 .tor of Museum, Albion Academy. Albion. Wis. 



Morris's "British Butterflies," Morris's "Nests and 

 Eggs of British Birds." Bree's " Birds of Europe" (all 

 colored plates), and other natural history, in exchange 

 for Shakesperiana ; either books, pamphlets, engravings, 

 or cuttings. — J. D. Barnett, Box 735, Stratford, Canada. 



I have Anodonta opahna (Weatherby), and many 

 ■other .'species of shells from the noted Koshkonong Lake 

 and vicinity, also from Western New York, and fossils 

 from the Marcellus shale of New York, which t would be 

 glad to exchange for specimens of scientific value of any 

 kind. I would also like to correspond with persons inter- 

 ested in the collection, sale, or exchange of Indian relics.— 

 D. E. Willard, Albion Academy, Albion, Wis. 



Will exchange ''Princetun Revie\^ 

 Miller's works on geology and other ; 

 iack numbers of " The Auk," "Ami 

 or other scientific periodicals or book 

 Keck, Chardon, Ohio. 



" I wish to exchange Lepidoptera ■ 

 .eastern and southern states. I w 

 for those found in other localit 

 Volga, Brookings Co., Dakota. 



Shells and curiosities for marine shells, curiosities or 

 aninerals address W. F. Lerch, No. 308 East Fourth St., 

 Davenport, Iowa. 



I want to correspond and exchange with a collector of 

 .teetles in Texas or Florida. — Wm. D. Richardson, 

 P.O. Box 223, Fredericksburg, Virginia. 



A collection of fifty unclassified shells for the best offer 

 in bird skins ; also skins of California birds for those of 

 birds of other localities. Address Th. E. Slevin, 2413 



for 1883, Hugh 

 ;ntific works, for 

 :an Naturalist," 



Write.— J. M. 



with parties in the 

 send western species 

 "—P. C. Truman, 



I ha 



St., Sa 

 forty vai 



o. Cal, 



eties of birds' egg-^, side blown, first 

 full data, which I will exchange for 



books, scientific journals, shells, and curios. Write ir 

 stating what you have to offer. — Dr. W. S. Strod 

 Eernadotte, Fulton County, III. 



A GAIN OF A POUND A DAY IN THE 

 CASE OF A MAN WHO HAS BECOME "ALL 

 RUN DOWN," AND HAS BEGUN TO TAKE 

 THAT REMARKABLE FLESH PRODUCER, 



SCOTT'S 



Fmulsion 



OF PURE COD LIVER OIL WITH 



Hypophosphites of Lime & Soda 



IS NOTHING UNUSUAL. ThIS FEAT 

 HAS BEEN PERFORMED OVER AND OVER 



AGAIN. Palatable as milk. En- 

 dorsed BY Physicians. Sold by all 

 Druggists. Avoid substitutions and 

 imitations. 



Mineral Lands. 



MANGANESE DEPOSITS. —A rich de- 

 post of Manganese is for sale. Apply to H. 

 N., care of Science, 47 Lafayette Place, New 

 York. 



GOLD-BEARING QUARTZ VEINS.— 

 Any one wishing to engage in gold mining will 

 learn of a newly discovered vein by applying to 

 H N., care of Science, 47 Lafayette Place, New 

 York. 



RED SLATE. — A valuable deposit of red 

 slate for sale. Apply to H. N., care of Science, 

 47 Lafayette Place, New York. 



■.-••■JOfift nftsriNos= 



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