July 3, 1879] 



NATURE 



233 



cieiit delicacy to measure every one -hundredth of horse-power. 

 With this instrument he can calculate the cost of the electric 

 light to the minutest detail. He has demonstrated that from 80 

 to 90 per cent, of energy is converted into light, and that six 

 electric lights are supplied from one horse-power at one-third the 

 cost of gas. He maintains that the problem of applying the 

 electric light to domestic use has been practically solved, but 

 admits that a great mass of detail remains to be worked out. He 

 has satisfied himself that platinum can be supplied in large 

 quantities so as to reduce the expense. 



The forests of Central Nevada appear (from the accounts of 

 Mr. Sargent, who visited the region last year, and writes about 

 them in Silliman's yournal for June) to be miserably poor in 

 extent, productiveness, and especially in number of species. Yet 

 they are of immense value, as regulating and protecting the rare 

 and uncertain streams on which the agriculture of Nevada 

 depends, and furnishing a large population with fuel and 

 lumber, a population practically cut off from outside supply. 

 Mr. Sargent laments the wasteful destruction of forest which 

 follows every new discovery of the precious metals in that region, 

 both on account of the immense age of these forests, and of the 

 impossibility of restoration ; and he thinks government should 

 check it. The central Nevada forests consist of but seven 

 species, the juniper (Juniperus californica, var. Utahensis) and 

 nut pine (Pinus tnonofhylla, Torr.), being the most common. 

 Mountain mahogany (C£rr«rt?-/a J Icdifolius) comes next, probably 

 the only North American wood heavier than water, and furnish- 

 ing the common and cheapest fuel. The other species are the 

 red cedar, the aspen, and two of pine. A comparison which Mr. 

 Sargent makes, of the arborescent vegetation of Nevada with 

 that of the region lying directly cast and west of the Great 

 Basin, brings out still more clearly the remarkable poverty of 

 the former. 



A VERY ingenious application of electricity to the purposes of 

 navigation has recently been effected by Mr. Henry A. Severn, 

 of Heme Hill, who has succeeded in producing a mariner's 

 compass which enables the captain or officer in charge to hear, 

 by the ringing of a bell, when the vessel is out of the ordered 

 course. The whole of the apparatus is contained in a small box 

 which is easily carried about, and is intended, as a rule, to be 

 placed in the captain's cabin. Over the card are two index 

 hands, which can be adjusted to any angle allowing of greater or 

 less deviation in steering to either the port or starboard side. 

 Assuming the captain, on quitting the deck, to have given in- 

 structions to steer the ship on a certain course, be sets the index 

 hands to a certain angle, allowing the steersman a given latitude 

 for deviation either to port or starboard of that course. Should 

 the ship be .steered off her course beyond the limit allowed on 

 either side an electric alarm-bell rings instantaneously and, 

 moreover, continues ringing until the right course is resumed. 

 The metal point on which the card is hung is insulated from the 

 compass bowl, and to it is attached a wire from one pole of a 

 small battery. About an inch above the card, placed parallel to 

 its sm-face and attached to its metal centre (which is insulated 

 from the needle) is an arm of metal reaching nearly to the edge 

 if the card. This arm is, therefore, in metallic communication 

 with the wire from the battery already referred to. The glass 

 lid of the compass has a short brass rod working within a tube 

 passing through it. These are severally attached to two brass 

 milled heads above the glass lid and to the two movable index- 

 hands beneath the glass. These are in metallic contact with the 

 brass-work of the compass, and this with the other pole of the 

 battery. Beneath the outer extremities of the index-hands are 

 suspended two pieces of platinum wire about three-quarters of 

 "n inch long. These hands can, by means of the two milled 

 iieads, be moved round to any position over any point of the 

 "ird. Hence they admit of being placed on either side and 



equally distant or otherwise from the end of the metal arm on 

 the card. It will thus be seen that whenever the platinum wires 

 come into contact with the metal arm on tlie card the circuit is 

 completed. The electric bell being placed in the circuit sounds 

 whenever such contact takes place. Two bells of different tone 

 can be used, and thus the instrument will indicate to the captain 

 whether the deviation in steering is to port or starboard. 



We have received an interesting yahresbcricht of the Natural 

 History Society of Wisconsin, which is evidently largely com- 

 posed of Germans, the Report being in that language. 



We have on our table the following books : — "The Human 

 Species," A. de Quatrefages (C. Kegan Paul); "Practical 

 Photography," Part I, O. E. Wheeler (Bazaar Office) ; 

 "Modern Meteorology" (Ed. Stanford); " Mechanics," Prof. 

 R. S. Ball (Longmans) ; " The Application of Generalised 

 Co-ordinates to the Kinetics of a Material System," H. W. 

 Watson and S. H. Burbury (Clarendon Press); "Galileo 

 Galilei," Karl von Gebler (Kegan Paul); "What is Truth," 

 John Coutts (F. Pitmann) ; "Sulphuric Acid and Alkali," 

 Vol. i., George Lunge (Van Voorst) ; " Elementary Arithmetic 

 and How to Teach It," G. Ricks (Isbister and Co.) ; "Supple- 

 ment to a Handbook of Chemical Manipulation," C. G. Williams 

 (Van Voorst); " Town and Window Gardening," C. M. Buckton 

 (Longmans) ; " Der Process Galilei's und die Jesuiten," Dr. F. H. 

 Reusch (Edw. Weber, Bonn); "Parasites, a Treatise on the 

 Entozoa of Man and Animals," T. Spencer Cobbold, M.D. 

 (Churchill); "Elements of South- Indian Palseography," A. C. 

 Burnett (Trlibner) ; " Twenty Lessons in Inorganic Chemistry," 

 W. G. Valentine (W. Collins) ; "Observed Lunar Distances,'' 

 John B. Pearson (Bell and Sons) ; " Floral Dissections," Rev. G. 

 Henslow (Edw. Stanford) ; " Contributions to our Knowledge 

 of the Arctic Regions," Part I (Edw. Stanford) ; " Proceedings 

 of the Aberdeenshire Agricultural Association," Sessions 1S78 ; 

 "A Manual of Scientific Terms," Rev. James Stormouth 

 (Maclachlan and Stewart, Edinburgh); "Hand List of Mol- 

 lusca in the Indian Museum," Part i, Godfrey Nevill (Calcutta); 

 "Chronological History of Plants" Charles Pickering (Trlib- 

 ner) ; "Report of New York State Survey, 1878," James F. 

 Gardner ; " Pontresina and its Neighbourhood," J. M. Ludvvig 

 (Stanford) ; " Description physique de la Republique Argen- 

 tine," Vols. ii. and v., and Atlas, &c.. Dr. H. Burmeister (Paris, 

 F. Savy) ; " British Birds," G. Peter Moore (J. van Voorst) ; " A 

 Hunting Expedition to the Transvaal," D. Fernandes das Nives 

 (Bell); "Origin of the Laws of Nature," Sir Edw. Beckett, 

 Bart. (S.P.C.K.); "Lectures on Practical Astronomy," Rev. 

 J. Challis (Deighton, Bell, and Co.); "Arithmetic," J. W. 

 Marshall (Marcus Ward) ; " Scientific Lectures," Sir John Lub- 

 bock (Macmillan and Co.); "Agricultural Botany, Turnip- 

 singling," A. Stephen Wilson (Smith, Aberdeen) ; " The Rights 

 of an Animal," E. B. Nicholson (Kegan Paul); "Com- 

 mercial Organic Analysis," Vol. i., Alf. Allan (Churchill) ; 

 "Demonology and Devil-Lore," 2 vols., M. D. Conway (Chatto 

 and Windus) ; " Atlas of Histolog)," Part S, Smith and Klein 

 (Smith, Elder). 



The additions to the Zoological Society's Gardens during the 

 past week include a Crested Pigeon (Ocyphaps lophotes) from 

 Australia, presented by the Rev. A. H. Glennie; two Lesser 

 Redpoles (Linota linaria), British, presented by Dr. Bree, 

 F.Z.S. ; a Common Lobster (Homarus vulgaris), British Seas, 

 presented by Mr. G. H. Jones, F.Z.S. ; two Black-tailed God- 

 wits (Limosa melanura), British, two Beautiful Parrakeets 

 (Psephotus pukherrimus) from Australia, four White Storks 

 (Ckoiiia alba), European, two Tuatera Lizards (Sphenodon 

 pitnctalus) from New Zealand, purchased ; two Geoffroy's Doves 

 (Peristera gcoffroii), three Spotted-billed Ducks (Anas poecilo- 

 rhyncha), three Australian Wild Ducks (Anas superciliosa), 

 three Chilian Pintails (Dafila spinkauda), bred in the Gardens. 



