ADDRESS. 9 



differing in diameter by the y^^^j^th or the tttJ ooth of an inch, were given 

 to his workmen, with the I'esult that a degree of accuracy inconceivable 

 to the ordinary mind became the rule of the shop. 



To render the consti-uction of accurate gauges possible Whitworth 

 devised his measuring machine, in which the movement was effected 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 mathematical-instrument 

 maker to become the common property of every machine shop. And not 

 only is the latest form of steam-engine, in the accuracy of its workman- 

 ship, 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 lias 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 accu- 

 rate measurement and patient, long-continued labour in the sifting of 

 numerical results.' The discovery of argon, for which Lord Rayleigh and 

 Professor Ramsay have been awarded the Hodgkin prize by the Smithsonian 

 Institution, affords a remarkable illustration of the truth of this remark. 

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

 weight, capacity, temperature, force, and energy, are amongst the founda- 

 tions of scientific investigation. 



In 1842 the British Association obtained the opportunity of 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 pendulum observations in various parts of 

 the world. They subsequently extended it into an observatory for com- 

 paring and verifying 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. 



This new departure afforded a means for ascertaining the advantages 

 and disadvantages of the several varieties of scientific instruments ; as well 

 as for standardising and testing instruments, not only for instrument- 

 makers, but especially for observers by whom simultaneous observations 

 were then being carried on in different parts of tJie world; and also for 

 training observers proceeding abroad on scientific expeditions. 



Its special object was to promote original research, and expenditure 

 was not to be incurred on apparatus merely intended to exhibit the 

 necessary consequences of known laws. 



The rapid strides in electrical science had attracted attention to the 



