an urban position.  The maximum both in town and country was reached on June 28, when in the town 105 pollen grains were deposited, and in the country 880 grains.  The number of grains deposited was found to vary much, falling almost to zero during heavy rain and rising to a maximum if the rain were followed by bright sunshine.  Mr. Blackley found that the severity of his own symptoms closely corresponded to the number of pollen grains deposited on his glasses.  Mr. Blackley devised some very ingenious experiments to determine the number of grains floating in the air at different altitudes.  The experiments were conducted by means of a kite, to which the slips of glass were attached, fixed in an ingenious apparatus, by means of which the surface of the glass was kept covered until a considerable altitude had been reached.  Mr. Blackley’s first experiment gave as a result that 104 pollen grains were deposited in the glass attached to the kite, while only 10 were deposited on a glass near the ground.  This experiment was repeated.  Again and again, and always with the same result, there was more pollen in the upper strata of the air than in the lower.

A very interesting experiment was performed at Filey, in June, 1870.  A breeze was blowing from the sea, and had been blowing for 12 or 15 hours.  Mr. Blackley flew his kite to an elevation of 1,000 feet.  The glass attached to the kite was exposed for three hours, and on it there were 80 grains of pollen, whereas a similar glass, exposed at the margin of the water, showed no pollen nor any organic form.  Whence came this pollen collected on the upper glass?  Probably from Holland or Denmark.  Possibly from some point nearer the center of Europe.

POTATO DISEASE.

A study of the terrible disease which so often attacks the potato crop in this country will serve, I think, to bring forcibly before you certain untoward conditions which may be called climatic, and which are attributable to fungoid spores in the air.

With the potato disease you are all, probably, more or less practically acquainted.  When summer is at its height, and when the gardeners and farmers are all looking anxiously to the progress of their crops, how often have we heard the congratulatory remark of “How well and strong those potatoes look!” Such a remark is most common at the end of July or the beginning of August, when the green part, or haulm, of the plant is looking its best, and when the rows of potatoes, with their elegant rich foliage and bunches of blossom, have an appearance which would almost merit their admission to the flower border.  The same evening, it may be, there comes a prolonged thunder storm, followed by a period of hot, close, moist, muggy weather.  Four-and-twenty hours later, the hapless gardener notices that certain of his potato plants have dark spots upon some of their leaves.  This, he knows too well, is the “plague spot,” and if he examine his plants