11 



health, attended Professor Gordon's classes in engineering, and was 

 busy with inventions of various sorts ; and particularly with a curious 

 boat, which, by means of paddles and legs reaching to the bottom, 

 was able to propel itself up a river, walking against the stream. 



In 1843 he was able to resume work as an engineer, and he went to 

 Millwall, to the works of Messrs. Fairbairn and Co., of London and 

 Manchester. He was not, however, able to remain with them for the 

 full time of his apprenticeship. Illness returned ; he was obliged to 

 go home ; and this illness proved the commencement of a period of 

 delicate health which lasted for years, and, indeed, produced a per- 

 manent effect on his whole life. 



During the months which he spent at Millwall, he was busy with 

 improvements in furnace construction for the purpose of prevention 

 of smoke. The gases of combustion were to be taken downwards 

 through the furnace instead of upwards ; and the fire bars were to be 

 tubes with water circulating through them. 



After his return to Glasgow he was obliged to confine himself to 

 work which did not involve bodily fatigue. He occupied himself 

 much with invention ; and particularly gave his attention to machines 

 for the utilisation of water power. 



He constructed a horizontal water-wheel, which he named a 

 Danaide, being an improvement on the Danaide of Manouri Dectot ; 

 and somewhat later, after much investigation and research, he 

 invented a wheel which, from the nature of its action, he called the 

 vortex water-wheel. This form of wheel was patented in 1850. It 

 was an important advance on water-wheels of previous construction. 

 The moving wheel was mounted within a chamber of nearly circular 

 form. The water, injected under pressure, was directed, by guide 

 blades, to flow tangentially to the circumference of the wheel ; and was 

 led through the wheel to the centre by suitably formed radiating 

 partitions. Thus the water yielded its kinetic energy derived from 

 one half of the fall, and its potential energy from the other half, to 

 the wheel by pressure on the radial partitions, as it passed inwards to 

 the centre, whence it quietly flowed away in the tail-race. A con- 

 siderable number of these wheels were designed by him for various 

 factories and for different purposes. They were made and supplied 

 by Messrs. Williamson Bros., of Kendal, and gave much satisfaction. 



In 1847 his mind was also busy with a question to which at a 

 later date he gave much thought and labour, and to the solution of 

 which he made contributions of great importance. On April 5 of 

 this year there appears a memorandum in his handwriting : — " This 

 morning I found the explanation of the slow motion of semi-fluid 

 masses such as glaciers." 



During 1848 his first three important scientific papers were 

 published. The first of these was on " Strength of Materials as 



