250 M. Arago's Biographical Memoir of James Watt. 



attached to the most suitable parts of the beam, so that in as- 

 cend ing it pulled one set of the cords, and in descending the 

 other, and so effectually, that all the work of his hand was 

 entirely superseded. For the first time, the steam-engine 

 went by itself ; and now no other workman was seen near it 

 but the fireman, who from time to time fed the furnace under 

 the boiler. 



For the cords of young Potter, the engineers soon substi- 

 tuted rigid vertical rods, which were fixed to the beam, and 

 armed with small pegs which either pressed from above down- 

 wards, or from below upwards, as required ; and thus turned 

 the different stopcocks and valves. These rods themselves 

 have since been replaced by other combinations ; but, how- 

 ever humbling the avowal, all these expedients are nothing 

 more than simple modifications of a contrivance suggested to 

 a child by his desire to join in the gambols of his youthful 

 companions. 



There exist in the museums of the curious, a considerable 

 number of machines from which industry had anticipated 

 great things, but which the expense of working and keeping 

 them in order has rendered little more than mere objects of 

 curiosity. Such, in all probability, would have been the fate 

 of Newcomen's machine, at least in those districts which were 

 not rich in fuel, had not the labours of Watt, which I must 

 now proceed to analyze, succeeded in conferring upon them 

 an unlooked-for perfection. This perfection must not be con- 

 sidered as the result of some fortuitous observation, or of 

 any single inspiration of genius : the author eff"ected it by 

 means of most assiduous labour, and by innumerable well 

 conceived and very delicate experiments. We may well say 

 that Watt took for his guide this celebrated maxim of Bacon, 

 " To write, speak, meditate, or act when we are not provided 

 yv\\)a. facts to direct our thoughts, is to navigate a coast full 

 of dangers without a pilot, and to launch into the immensity 

 of the ocean without either rudder or compass." 



There was in the museum of the University of Glasgow, a 

 small model of one of Newcomen's steam-engines which could 

 scarcely ever be made to work satisfactorily. Dr Anderson, 

 the Professor of Natural Philosophy, requested Mr Watt to 



