BY M.-------You asked me in last month's paper, " why no frosts, etc. had these destructive effects previous to 1846," which I might honestly answer by asking you another question. Is it a fact that previous to 1846 potatoes were not affected by both water and frost, so as to produce those diseases known as potato rot and potato blight? But in place of that I will answer you to the best of my recollection. I was born in Ireland, where, when a boy, I had often seen frosts in May cut down to the ground acres of potatoes that had made Six, eight, and even ten inches of growth, - such destruction being mostly upon low, boggy ground. I came to this country with father and family in 1820, and in 1831 was settled upon the farm on which I still reside. About 1841 or 1842 I broke up a piece of old meadow which I planted with potatoes. The summer and fall being wet, so that water for days would lie upon parts of it, I found at lifting time that wherever the water lay, that all the potatoes were rotted; while on the dry knolls they were sound. Several miles of under-draining was commenced about this time. It is about twenty-five years since I planted some two or three acres with Neshanock potatoes, upon a piece of boggy, coal formation soil.

Something prevented, so that the planting was kept back till July. One day, early in September, I was passing by my potatoes, when I found that a blight had passed over my beautiful patch, leaving it exactly like fields that I saw this summer blighted in Ireland. Now, sir, being entirely ignorant (and I confess it) of all the mysterious workings of funguses and spores, and the telegraphic manner in which they destroy fields of potatoes, I will tell you the conclusion that I came to respecting this blight. I said to myself - here is a bad job - these potatoes were too late planting. The slight frost last night and the hot sun to-day has fixed them - must plant so early after this that they will be ripe before the first chance of frost. Which conclusions I have carried out, and believe that that was the first and last potato blight that I ever saw upon the farm. While your scientific readers may prefer the microscope, I would advise your practical ones to keep an eye open upon Old Prob was the date fixed by our correspondent himself for the first appearance of the " frosts " so injurious to the potato. It is not uncommon to have frosts in September sufficient to destroy potato plants.

These cases have no doubt existed for many years, - but the potato disease, as we all now understand it, was not observed till 1845 on the British Isles, though we believe a year or so earlier on the Continent. - Ed. G. M.J