History certainly shows that the fuller application of great inventions has been slow, though Professor Nicholson somewhat over-estimates the mobility of labour and its ability to provide against impending changes. The story of the introduction of the power-loom discloses terrible sufferings among the hand-weavers of certain districts, in spite of the gradual manner in which the change was effected. The fact that along with the growth of the power-loom the number of hand-looms was long maintained, is evidence of the immobility of the hand-weavers, who kept up an irregular and ill-paid work through ignorance and incapacity to adapt themselves to changed circumstances.[189] In most of the cases where great distress has been caused, the directly operative influence has not been introduction of machinery, but sudden change of fashion. This was the case with the crinoline-hoop makers of Yorkshire, the straw-plaiters of Bedfordshire, Bucks, Herts, and Essex.[190] The suddenly-executed freaks of protective tariffs seem likely to be a fruitful source of disturbance. So far as the displacement has been due to new applications of machinery, it is no doubt generally correct to say that sufficient warning is given to enable workers to check the further flow of labour into such industries, and to divert it into other industries which are growing in accordance with the new methods of production, though much suffering is inflicted upon the labour which is already specialised in the older method of industry. Moreover, the changes which are taking place in certain machine industries favour the increasing adaptability of labour. Many machine processes are either common to many industries, or are so narrowly distinguished that a fairly intelligent workman accustomed to one can soon learn another. If it is true that "the general ability, which is easily transferable from one trade to another, is every year rising in importance relatively to that manual skill and technical knowledge which are specialised in one branch of industry,"[191] we have a progressive force which tends to minimise the amount of unemployment due to new applications of specific machinery.