This strain upon weaving, which had been tightening through the period of the great spinning improvements, acted as a special incentive to Cartwright, Horrocks, and others to perfect the power-loom in its application, first to woollen, then to cotton industries. Not until well into the nineteenth century, when steam power had been fully applied by many minor improvements, were the arts of spinning and weaving brought fully into line. The complete factory, where the several processes of carding, spinning, weaving (and even dyeing and finishing), are conducted under the same roof and worked in correspondence with one another, marks the full transition from the earlier form of domestic industry, where the family performed with simple tools their several processes under the domestic roof.[73] § 6. The history of these textile inventions does a good deal to dispel the "heroic" theory of invention--that of an idea flashing suddenly from the brain of a single genius and effecting a rapid revolution in a trade. No one of the inventions which were greatest in their effect, the jenny, the water-frame, the mule, the power-loom, was in the main attributable to the effort or ability of a single man; each represented in its successful shape the addition of many successive increments of discovery; in most cases the successful invention was the slightly superior survivor of many similar attempts. "The present spinning machinery which we now use is supposed to be a compound of about eight hundred inventions. The present carding machinery is a compound of about sixty patents."[74] This is the history of most inventions. The pressure of industrial circumstances direct the intelligence of many minds towards the comprehension of some single central point of difficulty, the common knowledge of the age induces many to reach similar solutions: that solution which is slightly better adapted to the facts or "grasps the skirts of happy chance" comes out victorious, and the inventor, purveyor, or, in some cases, the robber is crowned as a great inventive genius. It is the neglect of these considerations which gives a false interpretation to the annals of industrial invention by giving an irregular and catastrophic appearance to the working of a force which is in its inner pressure much more regular than in its outward expression. The earlier increments of a great industrial invention make no figure in the annals of history because they do not pay, and the final increment which reaches the paying-point gets all the credit, though the inherent importance and the inventive genius of the earlier attempts may have been as great or greater.