38 THE HISTORY OF [SECT. i. 



the construction and motion of the valves. The fifth was a method of connecting 

 the piston rod to the parallel motion. And the last, for the construction of fire 

 places, by which the smoke arising from the fire was to be consumed. In most of 

 these, however, he had been anticipated in practice. 



48. Another patent was obtained by Mr. Murray, in 1802, for a portable 

 engine ; but as it included some of the methods for which Messrs. Boulton and 

 Watt had patents, it was at their instance repealed in the following year. Boulton, 

 Watt and Co.'s portable engine was first constructed in 1806. 



1799. WILLIAM MURDOCH. 



49. Mr. Murdoch, a partner in the firm of Boulton, Watt and Co., obtained 

 in 1799 a patent for some new methods of construction, which consist of a mode of 

 boring the metallic cylinders and pumps more equably by means of an endless 

 screw, worked by a toothed wheel ; and a method of simplifying the construction 

 of the steam vessel and steam case, in engines formed on Mr. Watt's plan, by 

 casting the steam case of one entire piece, to which the cover and bottom of the 

 working cylinder are to be attached. He also proposed to cast the cylinder and 

 steam case in one piece of considerable thickness, and bore a cylindric interstice 

 between the steam case and steam vessel, leaving the two cylinders attached at one 

 end, and to close the other by a ring of metal. Another improvement included in 

 the patent was, a plan for simplifying the construction of the steam valves or 

 regulators of the double engine, by connecting together the upper and lower valves, 

 so as to work with one rod or spindle. The tube which connects them being 

 hollow serves as an eduction pipe to the upper end of the cylinder, and a saving 

 of two valves is effected ; and lastly, he adds a scheme for a rotary engine con- 

 sisting of two toothed wheels working in an air-tight vessel, which he imagined 

 would work with considerable power. Mr. Murdoch's modes of moving the valves 

 have added much to the simplicity and neatness of the double engine, and to his 

 skilful superintendence the steam engine owes many of its perfections ; and its 

 success in Cornwall was greatly aided by his activity, integrity, and resources for 

 overcoming the difficulties which the drainage of the mines presented. 



1801. DR. JOHN ROBISON; born 1739, died 1805. 



50. Dr. Robison, to whom the mixed mechanical sciences are so much 

 indebted for a more judicious combination of theory with practice than is to be 

 found in any preceding author, and for treating them in a more popular style, 

 seems to have bestowed much attention on the principles and construction of the 



