September 12, 1895] 



NATURE 



46: 



Government to undertake tidal observations at 500 stations on 

 the coasts of Britain. 



Another cognate instance is exemplified by a paper read at the 

 second meeting, in 1832, upon the State of Naval Architecture 

 in Great Britain. The author contrasts the extreme perfection 

 of the carpentry of the internal fittings of the vessels with the 

 remarkable deficiency of mathematical theory in the adjustment 

 of the external form of vessels, and suggests the benefit of the 

 application of refined analysis to the various practical problems 

 which ought to interest shipbuilders — problems of capacity, of 

 displacement, of stowage, of velocity, of pitching and rolling, of 

 masti.ng, of the effects of sails and of the resistance of fluids ; and, 

 moreover, suggests that large-scale experiments should be made 

 by (lovernment, to afford the necessary data for calculation. 



Indeed, when we consider how completely the whole habit of 

 mind of the populations of the Western world has been changed, 

 since the beginning of the century, from willing acceptance of 

 authority as a rule of life to a universal spirit of inquiry and ex- 

 perimental investigation, is it not probable that this rapid change 

 has arisen from society having been stirred to its foundations by 

 the causes and consequences of the French Revolution ? 



One of the earliest practical results of this awakening in France 

 was the conviction that the basis of scientific research lay in the 

 accuracy of the standards by which observations could be com- 

 pared ; and the following principles were laid down as a basis 

 for their measurements of length, weight, and capacity: viz. (i) 

 that the unit of linear measure applied to matter in its three 

 forms of extension, viz. length, breadth, and thickness, should 

 be the standard of measures of length, surface, and solidity ; (2) 

 that the cubic contents of the linear measure in decimetres of 

 pure water at the temperature of its greatest density should 

 furnish at once the standard weight and the measure of capacity.' 

 The metric system did not come into full operation in France till 

 1840 ; and it is now adopted by all countries on the continent of 

 Europe except Russia. 



The standards of length which w ere accessible in Great Britain 

 at the formation of the Association were the Parliamentary 

 standard yartl lodged in the Houses of Parliament (which was 

 destroyed in 1834 in the fire which burned the Houses of Parlia- 

 ment) ; the Royal Astronomical Society's standard ; and the 

 lO-foot bar of the Ordnance Survey. 



The first two were assumed to afl'ord exact measurements at a 

 given temperature. The Ordnance bar was f(jrmed of two bars 

 on the principle of a compensating pendulum, and afforded 

 measurements independent of temperature. Standard bars were 

 also disseminated throughout the country, n possession of the 

 corporations of various towns. 



The British Association early recognised the importance of 

 uniformity in the record of scientific facts, as well as the necessity 

 for an easy method of comparing standards and for verifj'ing 

 <lifrerences between instruments and apparatus required by 

 various observers pursuing similar lines of investigation. \\ its 

 meeting at Edinburgh in 1834 it caused a comparison to be made 

 between the standard bar at ^Vliertleen, constructed by Troughton, 

 and the standard of the Royal .\stronomical Society, and re- 

 ported that the scale " was exceedingly well finished; it was 

 a!>out Ttirrth of an inch shorter than the 5-feet of the Royal 

 Astronomical Society's scale, but it was evident that a great 

 number of minute, yet important, circumstances have hitherto 

 been neglected in the formation of such scales, without an 

 attention to which they cannot be expected to accord with that 

 degree of accuracy which the present state of science demands." 

 Subsequently, at the meeting at Newcastle in 1863, the Associa- 

 tion appointed a' committee to report on the best means of 

 providing for a uniformity of weights and measures with 

 reference to the interests of science. This committee recom- 

 mended the metric decimal system — a recommendation which 

 has been entlorse<l by a committee of the House of Commons in 

 the last session of last Parliament. 



British instrument-makers had been long conspicuous for 

 accuracy of workmanship. Indeed, in the eighteenth century 

 practical astronomy had been mainly in the hands of British 

 observers ; for although the mathematicians of France and other 

 countries on the continent of Europe were occupying the fore- 

 most place in mathematical investigation, means of astronomical 

 observation had been furnished almost exclusively by English 

 artisans. 



t The litre is the voUime of a kilogr.amme of pure water at it^ maximum 

 density, ami i*i slightly less than the litre was intended to be, viz. one cubic 

 <lecimetre. The weight of .a cubic .decimetre of pure water is 1*000013 

 kilogrammes. 



NO. 1350, VOL. 52] 



The sectors, quadrants, and circles of Ramsden, Bird, and 

 Gary were inimitable by continental workmen. 



But the accuracy of the mathematical-instrument maker had 

 not penetrated into the engineer's workshop. And the foundation 

 of the British Association was coincident with a rapid develop- 

 ment of mechanical appliances. 



At that time a good workman had done well if the shaft he 

 was turning, or the cylinder he was boring, " was right to the 

 ji^nd of an inch." This was, in fact, a degree of accuracy as fine 

 as the eye could usually distinguish. 



Few mechanics had any distinct knowledge of the method to 

 be pursued for obtaining accuracy ; nor, indeed, had practical 

 men sufficiently appreciated either the immense importance or 

 the comparative facility of its acquisition. 



The accuracy of workmanship essential to this development of 

 mechanical progress required very precise measurements of 

 length, to which reference could be easily made. No such 

 standards were then available for the workshops. But a little 

 before 1830 a young workman named Joseph Whitworth realised 

 that the basis of accuracy in machinery w as the making of a true 

 plane. The idea occurred to him that this could only be secured 

 by making three independent plane surfaces ; if each of these 

 would lift the other, they must be planes, and they must be true. 

 The true plane rendered possible a degree of accuracy beyond 

 the wildest dreams of his contemporaries in the construction of 

 the lathe and the planing machine, which are used in the 

 manufacture of all tools. 



His next step was to introduce an exact system of measurement, 

 generally applicable in the workshop. 



Whitworth felt that the eye was altogether inadequate to secure 

 this, and appealed to the sense of touch for affording a means of 

 comparison. If two plugs be made to fit into a round hole, they 

 inay differ in size by a quantity imperceptible to the eye, or to 

 any ordinary- process of measurement, but in fitting them into 

 the hole the difference between the larger and the smaller is 

 felt immediately by the greater ease with which the smaller 

 one fits. In this way a child can tell which is the larger of 

 two cylinders differing in thickness by no more than -soVirth of 

 an inch. 



Standard gauges, consisting of hollow cylinders with plugs to 

 fit, but differing in diameter by the yAirth or 'he TirJuiith of an 

 inch, were given to his workmen, with the result that a degree 

 of accuracy inconceivable to the ordinary mind became the rule 

 of the shop. 



To render the construction of accurate gauges possible, WTiit- 

 worth devised his measuring machine, in which the movement 

 was eflfected by a screw ; by this means the distance between 

 two true planes might be measured to the one-millionth of an 

 inch. 



These advances in precision of measurement have enabled the 

 degree of accuracy which was formerly limited to the mathe- 

 matical-instrument maker to become the common i)roperty of 

 every machine shop. And not only is the latest form of steam- 

 engine, in the accuracy of its workmanship, little behind the 

 chronometer of the early part of the century, but the accuracy 

 in the construction of experimental apparatus which has thus 

 been introduced has rendered possible recent advances in many 

 lines of research. 



Lord Kelvin said, in his Presidential Address at Edinburgh, 

 " Nearly all the grandest discoveries of science have been but 

 the rewards of accurate measurement .and patient, long-continued 

 labour in the sifting of numerical results." The discovery of 

 argon, for which Lord Rayleigh and Prof. Ramsay ha\e been 

 awarded the Hodgkin prize by the Smithsonian Institution, 

 affords a pregnant illustration of the truth of this remark. 

 Indeed, the provision of accurate standards not only of length, 

 but of weight, cap.acity, temperature, force, .and energy, are 

 amongst the foundations of scientific investigation. 



In 1842, the British .Association obtained the opportunity oi 

 extending its usefulness in this direction. 



In that year the Government gave up the Royal Observatory 

 at Kew, and offered it to the Royal Society, who declined it. 

 But the British .Association accepted the charge. Their first 

 object was to continue Sabine's valuable observations upon the 

 vibrations of a pendulum in various gases, and to promote pen- 

 dulum observations in different parts of the world. They subse- 

 (piently extended it into an observatory' for comparing and veri- 

 fying the various instruments which recent discoveries in physical 

 science had suggested for continuous meteorological and 'magnetic 

 observations, for observations and experiments on atmospheric 

 electricity, and for the study of solar physics. 



