There is nothing fortuitous or mysterious in inventive energy. Necessity is its mother, which simply means that it moves along the line of least resistance. Men like Kay, Hargreaves, Arkwright, Cartwright, set their intelligence and industry to meet the several difficulties as they arose. Nearly all the great textile inventors were practical men, most of them operatives immersed in the details of their craft, brought face to face continually with some definite difficulty to be overcome, some particular economy desirable to make. Brooding upon these concrete facts, trying first one thing then another, learning from the attempts and failures made by other practical men, and improving upon these attempts, they have at length hit upon some contrivance that will get over the definite difficulty and secure the particular economy. If we take any definite invention and closely investigate it, we shall find in nearly every case it has thus grown by small increments towards feasibility. Scientific men, strictly so-called, have had very little to do with these great discoveries. Among the great textile inventors, Cartwright alone was a man leading a life of thought.[75] When the spinning machinery was crippled in its efficiency by the crude methods of carding, Lees and Arkwright set themselves to apply improvements suggested by common-sense and experience; when Cartwright's power-loom had been successfully applied to wool, Horrocks and his friends thought out precisely those improvements which would render it remunerative in the cotton trade.