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�� ��Lo«} Raylcigh has been engaged upon a Study of the silver voltameter and ita applica- tion to the measurement of electrical currents. He finds that one ampere deposits four grama of silver per hour, and a sufficient amount can therefore be obtained for accurate weigh- ing in RAeen minutes. Pure nitrate or chlo- rate of silver gives the beat reaulu. Beetz has proposed a new form of Doniell cell, of grvat inlcni a I resistance. Fine alabaster plastcr- of-raris is mixed with concentrated sulphate- of-copper solution, and the copper electrode is fist'd in this at one end of a glass tube: the rest of the tube is filled with concentrated eulplialc of zinc and plaster-of-Paris, and the Kinc cU-ctrode is also embedded in this. The ends of the tube are filled with porafilue. This form of cell has been tried at the Jefferson physical Inboratorj- of Harvard UQiversity, and has been found an excellent siibetitute for the water-cell of zinc and copper for cliarging electrometers.
The lull in Uie progress of theoretical elec- tricity is probably the precursor of important ad<Iilions tn our knowledge ; for many invesli- gatora ari' at work, both at home and abroad, testing the new electrodjTiamic theory of light, ~' adding to our knowledge of mngnetiam. equipmentof physical laboratories in Amer-
., which has been one of the features of the
Lf At Cambridge as well as elsewhere in America, bids us hope for much sj'stematic littidy of the science of electricity, and pb_\8i- general. John TROwnitiixiK.
��Tkk lanil-ma|isnf Kuropeaiicountrie»are, asarule, lliad« under the ilireclion of the war departments oi ttiMe cuuntrlt^s. .\n<l under the direction uf 'iffic^rs of tl)F ftrmy apeelally detaile.l tor Ihit duty, wllh lh« aid of expert* iu the busineBa and In the arts iieccasarf to the Hurveyi and to the production of the cliiirw, who are employed from civil life, and also of enlisted widrers and non-com miisioned officers detaili-^l from the army.
For details on this subject, ilie committee refers to Um priuled notes gn Europeon surveys compiled and published in 18TQ, under the direction of one of its members, Gen. C. B. Comstock, U.S. engineers, as the most TOmplete comjvpndlutu on this subject known to them; also to some manuscript notes prepared by tlic committee from reports acid publications of later date.
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�� ��The hydrographic survej's of llie coasts of Europe appear in every country la be the woric of the naval establishment. On the coasts of the United EEog- dom the hydrography has been completed; and now two parlies in surveying vessels of the navy are con- stantly employed in re-sounding and examining chan- nels, harbors, and shoals, in order to correct the exisiiug admiralty charts. All this is done under direction of the ndinlralty.
Wliite the organization of the land and of the hy- drographic surveys in Europe are very perfect, your committee does not find that they offer any thing to improve that of the United States, except, perhaps, in showing the economy iu time and money of greater use of photography and of zincography tn the redno- tion and production of maps and charts. In Great Britain now the twenly-flve- in ch-lo-l he-mile map is published even earlier than those on smaller scales, all of which are reductions from the original manu- script maps surveyed and plotted on the twcnty-five- inch or nix-inch scale.
Early and cheap publications of results of opera- tions in the field, if they retain the accuracy of the original maps, are of great industrial and economic importance. The English maps of the ordnance survey are published and placed on sale as soon ai printed, and at very moderate prices.
Yonr committee would call Bttentloo, in this con- nection, to the report made by the National academy of sciences to congress In December, 1ST8, in whlcli the advantages of a consolidation of the then exist- ing surveys were pointed out. In that report, it was recommended thai surveys should Ite two in n umber, — the coast and interior Burvey, to be concenied with the trionguiation and mappiiig of the cuuiitry and its topography; and a geological survey, to undertake geological and economical investigations. It wonld be u part of the duty of the former survey to supply the maps tor the use of the geological survey ; and, In order to secure the co-ordination and hsrmoDious co- operation of the two surveys, it was recommended that the coast and Interior survey be Iranalerred to the interior department.
Congress adopted so much of llils I'ecommendation as related to the formation of a single geological sur- vey, but did not provide for the proposed transfer of the coast--stu-vey, nor make any other provision for the topi^raphic work necessary for (lie geological snrrey. The result has been (hat these two surveys do nut co-operate as they should, Thd chief of the geological survey has also found It necessary to em.- ploy large corps of men in trigonometric meaauro-
Tour committee does not feel entire confidence that the union of these two surveys under either one of the executive departments, would, without other measures, necessarily lead to that unity of work which la desirable. It therefore recommends certain further legislative measures, the occasion for which will be mode clear by a review of the work done by these several organ! ration a ; but Its members are entirely clear in the opinion that some one of the ex- ecutive departments should control both. It Is for
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