By the year 1760 potatoes appear to have become a common crop all over the country; and by 1770 they seem to have attained to that importance as a staple article of food for the common people which they have ever since maintained.[82] The importance of the introduction of this valuable article of food, in respect both of the weal and the woe of the Highlands, cannot be over-estimated. As an addition to the former scanty means of existence it was invaluable; had it been used only as an addition the Highlanders might have been spared much suffering. Instead of this, however, it ere long came to be regarded as so all-important, to be cultivated to such a large extent, and to the exclusion of other valuable productions, and to be depended upon by the great majority of the Highlanders as almost their sole food, that one failure in the crop by disease or otherwise must inevitably have entailed famine and misery. For so large a share of their food did the common Highlanders look to potatoes, that, according to the _Old Statistical Account_, in many places they fed on little else for nine months in the year. The first remarkable scarcity subsequent to 1745 appears to have been in the year 1770,[83] arising apparently from the unusual severity of the weather, causing the destruction of most of the crops, and many of the cattle. That, however, of 1782-83 seems to have been still more terrible, and universal over all the Highlands, according to the _Old Statistical Account_. It was only the interference of government and the charity of private individuals that prevented multitudes from dying of starvation. Neither of these famines, however, seem to have been caused by any failure in the potato crop from disease, but simply by the inclemency of seasons. But when to this latter danger there came subsequently to be added the liability of the staple article of food to fail from disease, the chances of frequently recurring famines came to be enormously increased. About 1838 potatoes constituted four-fifths of the food of the common Highlanders.[84] However, we are anticipating. It is sufficient to note here as a matter of great importance in connection with the later social history of the Highlands, the universal cultivation of the potato sometime after the middle of the eighteenth century. Even during the latter part of last century, potato-disease was by no means unknown, though it appears to have been neither so destructive nor so wide-spread as some of the forms of disease developed at a later period. New forms of disease attacked the root during the early part of the present century, working at times considerable havoc, but never apparently inducing anything approaching a famine. But about 1840, the potato disease _par excellence_ seems to have made its first appearance, and after visiting various parts of the world, including the Highlands, it broke out generally in 1845, and in 1846 entailed upon the Highlands indescribable suffering and hardship.