August 4, 1892] 



NATURE 



\n 



practical unit of electrical energy, and be called the watt. (It 

 equals 2640 foot-pounds, or a trifle over a foot-ton. ) 



(5) That the present Board of Trade unit be called a kilowatt. 



(6) That the ordinary unit of power be a kilowatt per hour 

 [It equals about 4/3rds of a horse-power, more accurately 

 1000 jp^ 



746 



(7) That it is convenient to retain the name joule in its 

 present sense of a volt-coulomb, or ten million ergs, for use in the 

 science of heat ; since heat-capacities are conveniently expressed 

 in joules per degree ; and it will be handy to remember that a 

 volt-ampere generates one joule of heat per second. 



(8) That the name coulomb be affixed to the electrostatic 

 unit of quantity [for academic purposes]. 



(9) That a name be given to unit magnetic flux or total in- 

 duction, and that the name weber is suitable. 



(10) That the most convenient size for the weber is 10* cg.s. 

 units or " lines " (since the rate of change of this through a 

 circuit is equal to the induced voltage). 



(11) That a name be given to unit magnetic potential or 

 magnetomotive force, and that the name gauss is suitable. 



(12) That the handiest size for the gauss is one ampere-turn. 



(13) That a name be given to the ratio of the weber to the 

 gauss, or unit of permeance, or self-induction per turn of wire. 

 [If the above resolutions were adopted, this unit would be 

 4ir X 10^ cg.s. units, or | secohm per turn.] 



(14). That intensities of field be expressed in gausses per unit 

 length, and densities of induction in webers per unit area (leaving 

 the length or area unit open for practical convenience to arrange). 



No doubt many of these recommendations have been made 

 before. Mr. Preece has often urged the change of farad, so 

 that I hope there will be no difficulty about that. 



I find that my magnetic suggestions are very similar to those 

 suggested by Prof. Perry in his modified letter to the Committee 

 as published in the Electrician, vol. xxvii. p. 355 [July 31, 

 1891], and received there with approving editorial comments. 

 The accordance between our suggestions is satisfactory, and 

 makes it likely that they are such as engineers may be satisfied 

 with and be willing to adopt. I need hardly say that I lay no 

 stress upon the particular naiiies here proposed. In choosing 

 them I have been influenced by such trivial considerations as the 

 selection of a monosyllable to correspond with volt, and a dis- 

 syllable to correspond with ampere or coulomb, 



[With regard to Prof. Perry's footnote concerning college in- 

 struction and use of cg.s. units, I suppose systems of teaching 

 differ, but a senior student ought to be taught to deal with con- 

 crete quantities in so familiar a manner that no possible ad- 

 mixture of units can be any puzzle to him, nor involve anything 

 worse than a little tiresome arithmetic] 



Mechanical Units. 

 There are several quantities in dynamics beside the joule and 

 the watt for which brief names would be advantageous. I do 

 not propose to discuss these fully now, but the present oppor- 

 tunity might be utilized by agreeing to at least one unit, that of 

 pressure, viz., the "atmosphere" ; which might be defined as 

 10" cg.s., or dynes per square centimetre, and stated to be 

 equal to the pressure of a column of mercury 75 centimetres 

 high at a specified temperature. The inconvenient pressure, 76 

 centims., might be spoken of as a Regnault atmosphere. I be- 

 lieve that a smaller unit of pressure, for instance, the micro- 

 atmosphere or " barad," might also be usefully named. These 

 pressure units will be useful for expressing energies per unit 

 volume also, and the " barad, "or whatever other name is decided 

 on for the erg per cubic centimetre, is of reasonable magnitude 

 for many purposes. 



Oliver J. Lodge. 



THE INSTITUTION OF MECHANICAL 

 ENGINEERS. 



T^HE annual summer meeting of the Institution of Mechanical 

 ■^ Engineers, held last week at Portsmouth, was a successful 

 gathering in regard to numbers present and the attendance at the 

 excursions; but the business part of the meeting, which consists 

 of the sittings at which papers are read, was of a rather tame 



character. The following is a list of the papers on the 

 agenda : — 



On Shipbuilding in Portsmouth Dockyard, by Mr. William 

 H. White, C.B., F.R.S., Director of Naval Construction and 

 Assistant Controller of the Navy. 



On the Applications of Electricity in the Royal Dockyards 

 and Navy, by Mr. Henry E. Deadman, Chief Constructor, 

 Portsmouth. 



Description of the Lifting and Hauling Appliances in Ports- 

 mouth Dockyard, by Mr. John T. Corner, R.N., Chief En- 

 gineer, Portsmouth. 



Description of the New Royal Pier at Southampton, by James 

 Lemon, J. P., Mayor of Southampton. 



Description of the Portsmouth Sewage Outfall Works, by Sir 

 Frederick Bramwell, Bart., D.C.L., LL.D., F.R.S., Past- 

 I President. 



Description of the New Floating Bridge between Portsmouth 

 and Gosport, by Mr. H. Graham Harris, of London. 



Description of the Southampton Sewage Precipitation Works 

 and Refuse Destructor, by Mr. William B. G. Bennett, Borough 

 Engineer and Surveyor. 



Description of the Experimental Apparatus and Shaping 

 Machine for Ship Models at the Admiralty Experiment 

 I Works, Haslar, by Mr. R. Edmund Froude, of Haslar. 



Description of the Pumping Engines and Water Softening 

 Machinery at the Southampton Water Works, by Mr. William 

 Matthews, Waterworks Engineer. 



Mr. Matthews' paper was adjourned, and that by Mr. Froude 

 was not read, as time ran short. This was much to be re- 

 gretted, as the Haslar experimental works are one of the most 

 interesting of all our establishments set apart for scientific investi- 

 gation. It is to be hoped, now Mr. Froude has broken the ice, 

 that he will contribute a fairly complete descriptive paper to the 

 Institution of Naval Architects, where he would naturally find 

 a more appreciative audience than amongst the members of a 

 society devoted more exclusively to mechanical engineering. 

 Although there was not time for the reading of the paper, Mr. 

 Froude very good-naturedly stopped and explained to some of 

 those present the working of the apparatus which he had brought 

 for the purpose of exhibition, together with the large wall 

 diagrams that had been prepared expressly for illustrating the 

 paper. 



On the members assembling in the Town Hall on July 26, Dr. 

 Anderson, the President, occupied the chair, and the usual 

 formal business having been disposed of, Mr. White's paper 

 was read. This was chiefly of a historical character, the author 

 going back to the year 1212, when the sheriff of the county of 

 Southampton was ordered to enclose the King's Dock by a 

 strong wall, and to provide suitable storehouses. A dockyard, 

 properly so called, was not, however, founded until the reign of 

 Henry VIII., so it was second in point of antiquity to Woolwich 

 Dockyard. The latter was closed in 1869, " so that Portsmouth 

 Yard is now," Mr. White says, "the oldest as well as the most 

 important in existence." We do not know whether Mr. White 

 means by this that it is the oldest in existence in Great Britain, 

 or in the whole world. In 1540 the total area was 8 acres. Until 

 nearly the end of last century there was no basin in which ships 

 could lie while completing or repairing, and the dock accommo- 

 dation was poor, but about that time a basin of 2 J acres and six 

 dry docks were constructed. At that time the yard area was 90 

 acres. In 1843-50 a steam factory was added, and another 

 basin of 7 acres, besides four docks ; the total area of the dock- 

 yard being 115 acres. The effect of steam on the navy is well 

 illustrated by the extensions that took place about 1864, when 

 the area of the Dockyard was more than doubled. A fitting- 

 out basin of 14 acres, a rigging basin of the same size, and a 

 repairing basin of 22 acres, were made. There is also a tidal 

 basin of 10 acres The extent of Portsmouth Dockyard is now 

 nearly 300 acres. 



Mr. Deadman's paper was also largely of an historical nature, 

 giving many interesting details of the introduction of electricity 

 into the navy. Among the most notable features in the appli- 

 cation of electricity to naval purposes are the temporary instal- 

 lations used for interior lighting during the building and finishing 

 of the vessel. The estimated cost of electric lighting during 

 the period of building the Royal Arthur was £\2<x>. This 

 would be about the same sum as would be required were candles 

 used, but naturally electricity affords a far superior light, and it 

 is to its use that is due much of the quickness with which the 



NO. II 88, VOL. 46] 



