811 



WEIGHTS AND MEASURES, STANDARD. 



WEIRS. 



842 



verse to the axis of the bar, and two lines at nearly the same interval 

 parallel to the axis of the bar. The measure of length is given by the 

 interval between the middle transversal line at one end and the middle 

 transversal line at the other end, the part of each line which is 

 employed being the point midway between the longitudinal lines. 

 The other transversal lines were used in the operations of comparison 

 only for assigning the scales of the micrometers. 



The committee having carefully examined the numerous bars placed 

 at their disposal by Mr. Sheepshanks, agreed in considering the bars 

 denominated by him bronze 19 and bronze 28, as exact copies of the 

 imperial standard, and they resolved that bronze 19 should hence- 

 forward be regarded as the new national standard. 



The final report of the committee addressed to the Lords Comrnis- 

 sioners of her Majesty's Treasury was signed on the 28th of March, 

 1854. The following are a few extracts from this important document : 



19. " The report of 1841 recommended (article 5) that, besides the 

 legal standard, there should be prepared four copies, to be deposited in 

 places to be afterwards determined. 



20. " The expansions of these bars corresponding to a given change 

 of temperature had been sufficiently determined in the course of the 

 experiments ; and it was then judged expedient, instead of stating the 

 difference in length of the selected bars at the same temperature, to 

 infer the difference of temperature which would cause all to represent 

 the same length, by the application of which it would be possible to 

 assign the specific temperature at which each bar represents precisely 

 the length of one yard. Thus it was found that the length of one yard 

 as given by the lost imperial standard, is represented with no sensible 

 uncertainty, except in the measures of the imperial standard itself, 

 by the following bars, at the temperatures placed opposite to them. 



. Bronze 19 or No. 

 Bronze 20 or No. 

 Bronze 2 or No. 

 Bronze 7 or No. 

 Bronze 10 or No. 

 Bronze 28 or No. 



1, at 62-00 Fahrenheit. 



2, at 61-94 Fahrenheit. 



3, at G2'-10 Fahrenheit. 



4, at 61-98 Fahrenheit. 



5, at 62 5 -16 Fahrenheit. 

 C, at 62'-00 Fahrenheit. 



21. "The degrees of temperature for the use of these standards are 

 defined aa proportional to the corresponding apparent increase of 

 volume of quicksilver in the thermometer tube ; the degree 32 repre- 

 senting the freezing point of water; and the degree 212 representing 

 the temperature of steam under Laplace's standard atmospheric pres- 

 sure, or the atmospheric pressure corresponding to the following 

 number of inches in the barometric reading reduced to 32 Fahr. : 

 29-9218 + 0-0766 x cosine (2 latitude) +0-00000179 x height in feet 

 above the sea ; and the degree 62 denoting the temperature which 

 produces in quicksilver an apparent expansion equal to ^ of the 

 expansion between 32 and 212; and so in proportion for other 

 degrees. 



23. " We propose that the bar No. 1 be adopted by the legislature 

 as the parliamentary standard of one yard ; that Nos. 2, 3, 4, 5 be 

 adopted as parliamentary copies ; and that No. 6 be retained by some 

 officer of the government for the comparison of other bars, or for other 

 scientific purposes in which reference to the standard may seem to be 

 required. 



35. " After careful consideration we recommend : 



" That the copy of length standard, No. 2, and the copy of weight 

 standard P.O., No. 1, be deposited in the Royal Mint. 



" That the copy of length standard, No. 3, and the copy of weight 

 standard, P.C., No. 2, be transferred to the Royal Society. 



" That the copy of length standard, No. 5, and the copy of weight 

 standard, P.C., No. 3, be deposited in the Hojal Observatory of 

 Greenwich. 



" That the copy of length standard, No. 4, and the copy of weight 

 standard, F.C., No. 4, be immured in the cill of the recess on the 

 east side of the lower waiting hall in the New Palace at Westminster. 



40. "After due consideration of this question, referring to the 

 reasons explained in Chapter II., of the report of 1841, December 21, 

 we adhere to the recommendation contained in that chapter, and 

 embodied in Articles 1 and 2 of the same report, that no reference 

 be made to natural elements for the values represented by the 

 standards. , 



41. " We consider the ascertaining of the earth's dimensions and of 

 the length of the seconds pendulum in terms of the standard length, 

 and of the weight of a certain volume of water in terms of the 

 standard weight, as philosophical determinations of the highest import- 

 ance, to the prosecution of which we trust that her Majesty's Govern- 

 ment will always give their most liberal assistance ; but we do not 

 urge them on the government at present as connected with the con- 

 servation of standards." 



The Lords Commissioners of the Treasury adopted the report of the 

 committee, and a bill was introduced into parliament relative to the 

 new standard weights and measures. This bill received the royal 

 assent on the 30th of July, 1855. It is styled an Act for legalising 

 and preserving the restored standards of weights and measures. In 

 the preamble of the bill allusion is made to the provisions in the act 

 5 Geo. IV. c. 74, for legalising and ensuring the restoration of the 

 standards. After referring to the destruction of the standards by the 

 fire of the Houses of Parliament, and to the doubts entertained by 



scientific men respecting the adequacy of the methods provided by the 

 said act for their restoration, it then announces the labours of the com- 

 mittee of weights and measures, describing the construction of the 

 new standards of weights and measures, and their parliamentary 

 copies, and specifies the places in which they have been respectively 

 deposited. It then proceeds thus : 



"And whereas it is expedient to legalise the standards so con- 

 structed, and to provide for the preservation thereof : Be it therefore 

 enacted by the Queen's most excellent Majesty, by and with the advice 

 and consent of the lords spiritual and temporal and commons in this 

 present parliament assembled, and by the authority of the same as 

 follows : 



" I. So much of the said act of the fifth year of king George the 

 Fourth, as relates to the restoration of the imperial standard yard, 

 and of the standard troy pound respectively, in case of loss, destruction, 

 defacement, or other injury, shall be repealed. 



" II. The straight line or distance between the centres of the two 

 gold plugs or pins in the bronze bar deposited in the office of the 

 Exchequer, as aforesaid, shall be the genuine standard of the measure 

 of length called a yard, and the said straight line or distance between 

 the centres of the said gold plugs or pins in the said bronze bar (the 

 bronze being at the temperature of sixty-two degrees by Fahrenheit's 

 thermometer), shall be and be deemed to be the imperial standard yard. 



" VII. If at any time hereafter, the said imperial standard yard and 

 standard pound avoirdupois respectively, or either of them, be lost, 

 or in any manner destroyed, defaced, or otherwise injured, the com- 

 missioners of her Majesty's Treasury may cause the same to be restored, 

 by reference to, or adoption of, any of the copies so deposited as afore- 

 said, or such of them as may remain available for that purpose." 



For an account of the restoration of the standard of weight, we 

 must refer the reader to a paper by Professor Miller, printed in the 

 ' Transactions of the Royal Society,' for 1856 (' On the construction of 

 the New Imperial Standard Pound, and its Copies of Platinum ; ' and 

 ' On the Comparison of the Imperial Standard Pound with the Kilo- 

 gramme des Archives,' ' Phil. Trans.,' vol. cxlvi., pp. 753-946). We 

 shall merely quote from the new act the following extracts relating to 

 the standard of weight : 



" I. So much of the said act of the fifth year of king George the 

 Fourth, as relates to the restoration of the standard troy pound, in case 

 of loss, destruction, defacement, or other injury, shall be repealed. 



" III. The said weight of platinum marked P.S., 1844, 1 lb., de- 

 posited hi the office of the Exchequer, as aforesaid, shall be the legal 

 and genuine standard measure of weight, and shall be and be denomi- 

 nated the imperial standard pound avoirdupois, and shall be deemed to be 

 the only standard measure of weight from which all other weights and 

 other measures having reference to weights' shall be derived, computed, 

 and ascertained, and one equal seven-thousandth part of such pound 

 avoirdupois shall be a grain, and five thousand seven hundred and 

 sixty such grains shall be, and be deemed to be, a pound troy. 



" VII. If at any time hereafter the said imperial standard pound 

 avoirdupois be lost, or in any manner destroyed, defaced, or otherwise 

 injured, the commissioners of her Majesty's Treasury may cause the 

 same to be restored by reference to, or adoption of, any of the copies so 

 deposited as aforesaid, or such of them as may remain available for 

 that purpose." 



WEIR, or WEAR, is a dam erected across a river, either for the 

 purpose of taking fish, of conveying a stream to a mill, or of maintaining 

 the water at the level required for the navigation of it. 



The erection of weirs across public rivers has always been considered 

 a public nuisance. Magna Charta (c. 23) directs that all weirs for the 

 taking of fish should be put down except on the sea-coast. By the 12 

 Edw. IV. c. 7, and other subsequent acts, weirs were treated as public 

 nuisances, and it was forbidden to erect new weirs, or to enhance, 

 straighten, or enlarge those which had aforetime existed. Hence in a 

 case where a brushwood weir across a river had been converted into a 

 stone one, whereby the fish were prevented from passing except in 

 flood-time, and the plaintiff's fishery was injured, this was considered 

 to be a public nuisance, although two-thirds of the weir had been so 

 converted without interruption for upwards of forty years. And it was 

 laid down, that though a twenty years' acquiescence might bind parties 

 whose private rights only were affected, yet that no length of time can 

 legitimate a public nuisance. 



The provision of the Roman law as to the maintenance of public 

 rivers (Uumina publica) against any impediment to navigation, or 

 against any act by which the course of the water is changed, are con- 

 tamed in the Digest (43 tit. 12,13). 



WEIRS. The constructions, whether of stonework, timber, or earth, 

 by means of which the waters of a river are retained to a given height, 

 or are diverted in any required direction, are known in the arts by the 

 name of weirs, or dams ; and they are principally used for the purposes 

 of creating mill-heads, artificial navigations, or head-waters for irriga- 

 tions. They may either be placed directly across a stream, or in the 

 line of its flow ; and when placed in the latter direction, they may be 

 made to regulate the height of the stream by the level of their crown, in 

 which case the weirs are called waste weirs, or tumbling bays, because 

 the excess of the waters, beyond the quantity necessary to keep the 

 surface up to the level of the crown, falls over the weir, and escapes 

 through the byewash, without producing any useful effect, 



