ATMOSPHERIC CONDITIONS DURING CYCLONES.

REVERTING to the terrible cyclones in Iowa, Nebraska, Kansas, and Missouri on Sunday, June 12, an illustration of the general atmospheric conditions in that region on that day may be of interest:

Here we find an intelligible illustration of the fact that opposing currents of air strongly contrasted in temperature, encountering each other, establish a rotary movement from their collision, attended by the formation of hail, the induction of violent winds, and the precipitation of frequently torrential rain.

These disturbances are not, properly speaking, cyclones; they are merely local tempests, more or less violent, of cyclonic character, and the probability of their occurrence can only be predicted in a general way from the general weather conditions. In the illustration we find decided contrasts in temperature and opposing winds. The arrow (2) probably indicates the direction of the line of meeting. The arrow (1) points to a then existing area of low pressure, the region illustrated being in its south-east quadrant. The observations were made at 2.30 P. M., Cincinnati time. The despatches referring to North-eastern Missouri say

that between 4 and 5 P. M., local time, three disturbances dealt death and destruction in as many paths. The first started at Savannah (a), passing through Flag Springs (6) and King City (c) with great destructive force and entailing loss of human lives. Another started at Windsor (d); another in the vicinity of Rosendale (e). In all these instances their course was north-eastward, which an examination of the history of a great number of tornadoes in different portions of the United States duing the past eighty years establishes as the general course— -that is, eastward, with more or less deflection toward the north. And here a remark of some practical value might be suggested. Persons seeing a tornado approaching at some distance, and from the west, and bearing the above in mind, may reasonably hope to escape its vortex by running to the southward. The question whether these tremendous operations of Nature occur more frequently now than formerly is an open one. That our climate is undergoing modification, because these terrific and often fatal disturbances so frequently occur as far north as Kansas, Missouri, and Iowa, remains to be proven. Although tropical, it is not established that these storms were ever confined to the tropics. In the earlier and sparsely populated period of the country they very likely occurred, being produced by the same causes, which existed then as now, but there was then no telegraph and no newspaper to carry the news.

GLOBULAR LIGHTNING.

AN eye-witness states that in the summer of 1859, while a class of scholars of what was then known as the Old Brick Schoolhouse, of East Whitby, in the county of Ontario, were seated in the gallery in the classroom, a ball of fire about eight inches in diameter was seen to slip through the stovepipe, the bottom portion of which had been taken away with the stove, and strike the floor. It then moved in a zigzag direction, and finally disappeared, having done no harm, and leaving no evidence of its presence beyond very slightly scorching the floor where it first struck.

Mr. Fitzgerald, of county Donegal, Ireland, saw a globe of fire in the air descend gradually along the crown of a ridge and down into the valley, where it drifted along a boggy surface, occasionally disappearing in the soil, but reappearing farther on. It finally flew across the stream, and buried itself and disappeared in the peat-bank. Its total duration was about twenty minutes. It appeared about two feet in diameter at first, but gradually diminished to three inches. The sky was clear at the time. Wherever it touched the ground in its course it ploughed up the earth to a depth of several feet.

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PLANTS AS WEATHER-PROPHETS.

HERR HANNEMAN, inspector of the Botanical Gardens at Proskau, Germany, has observed that several plants may be used as weather-prophHe finds that Convolvulus arvensis, the common English bindweed, and Anagallis arvensis, the English pimpernel, spread their leaves at the end of wet weather, while the different species of clover contract them. Stellaria media, the chickweed, at nine o'clock in the morning, if the weather is clear, straightens its flowers, spreads its leaves, and keeps awake until noon; if, however, there is rain in prospect, the plant droops and its flowers do not open. If they open a little, the coming rain will be of short duration. The same with Pimpinella saxifraga. Calendula pluvialis, the marigold, opens between six and seven in the morning, and generally keeps awake until four in the afternoon. In such cases the weather will be steady; if, on the other hand, it has not opened by seven o'clock in the morning, you may that day look for rain.

Sonchus arvensis and Oleraceus, the hog-thistles, indicate fine weather for to-morrow if the head of the blossom closes for the night; rain, if it remains open. Again, rain is certain if Hibiscus trionum, the bladder ketmia, does not open its blossoms; if Carduus cicalis, the stemless thistle, closes; if clover and most allied kinds droop their leaves. Also, if Lampsana communis, the nipplewort, does not close its blossoms for the night; if Draba verna, the whitlow-grass, lets its leaves hang drooping; if Galium verum swells and exhales strongly; also, if birches scent the air. Anemone ranunculoides, the crowfoot anemone, tells the coming rain by closing its blossoms, while Anemone mentaisa carries its flowers erect when the weather is fine, and drooping when overcast.

WHEN clouds are observed to break up into fragments and gradually to dissolve by evaporation, it indicates that the region of the atmosphere in which they float is under-saturated with moisture, and prognosticates dry weather. On the contrary, after a continuance of dry weather, when clouds are observed to form, or, when previously formed, are observed to increase in bulk and density, and also when small, detached clouds unite together and form larger clouds, it indicates that the causes immediately instrumental in the formation of clouds are in operation, and prognosticates that wet weather will soon follow.

INSECTS AS WEATHER-PROPHETS.

PINEY FALLS, TENN., is wonderfully productive of insects, especially red or brown ants; in many places the ground seems to be full of these indefatigable little workers. Near our residence is a small piece of low, boggy ground, which is generally dry except during heavy rain. I have frequently seen these little bogs literally swarming with ants. While passing over this ground one warm, pleasant morning, I observed what appeared to be a reddish streak or stripe, not unlike a two-inch-wide ribbon, lying close to the ground, having several crooks or curves, leading from the bog to higher ground, ending in a heap of rubbish at a distance of perhaps twenty feet. On a close examination this dark stripe proved to be a moving mass of small red ants, all hurrying one way, making all possible speed; no stragglers were seen out of this uniform strip, which seemed to contain millions. After watching this extraordinary exodus for half an hour, the rear end began to shorten, until the last travellers disappeared in the heap of rubbish, at which time large drops of rain began to fall, although a half hour before the sky was clear, with no visible signs of rain. But it had now become clouded, the rain soon fell in torrents, and in two hours the bog was mostly submerged.

PREDICTING GRASSHOPPER-INVASIONS.

PROFESSOR ABBE has recently proposed a theory of the grasshoppermigration which is said to account for most of the phenomena that have been observed in connection therewith. He explains that the grasshopper is an insect at home and comfortable only in a rather dry atmosphere, and possibly a diminished atmospheric pressure; air that is either too dry or too moist is equally liable to make the insect uncomfortable, and in either case he seeks relief in flight, not knowing whither he shall go. Now, the very dry winds are the westerly winds, that bear him rapidly eastward to the Missouri and Mississippi Valleys. The very moist winds are the south and south-east winds of the Mississippi Valley, that bear him or his progeny in the next year back to his original breeding-grounds.

THE date of the spring arrival of swallows (not martins) at Quebec, Montreal, and Ottawa varies each year from the 10th to the 25th of April.

THE GREAT COMET OF 1881.

MANY late watchers throughout North America in the wee sma' hours of Thursday, June 23, 1881, were surprised at the vision of a large, bright comet very near the star Capella, one of the brightest in the heavens. On May 31 the emperor of Brazil had telegraphed to the French Academy of Sciences that one had been seen from the southern hemisphere, and three days later Dr. Gould, a United States astronomer stationed at Cordova, in the Argentine Republic, announced its discovery from there. At that time the comet was south of the sun, and could not be seen either from Europe or North America. On June 23 its presence near Capella was telegraphed throughout the world, and on Thursday night and Friday morning it was sought out by tens of thousands of eyes, and its position noted. It had travelled north-in the direction of its tail, so to speaksome three hundred thousand miles in the twenty-four hours. For a few days it grew brighter, and then gradually departed from sight, being visible to the naked eye altogether some forty-eight days, its rate of travel being some three hundred thousand miles daily. Its nucleus is estimated at one thousand miles in diameter; the inner head at the envelope, twelve thousand miles; the coma, vastly more than that; and the tail, at least four million miles in length.

It is asserted by astronomers that the heavens are full of comets, whose number is legion, only a small proportion of them coming within the range of the telescope. It is stated that during the Christian era some five hundred have been seen by the naked eye-an average of one to every four years; that during the present century, now in its third quarter, seventeen have been seen; while in the eighteenth century the number was thirty-six.

Perhaps the most popular description of a comet is that given by Professor Newcomb, who says: "Comets bright enough to be noticed with the naked eye consist of three parts, which, however, are not completely distinct, but run into each other by insensible degrees. These are the nucleus, the coma, and the tail. The nucleus is the bright centre, which, to the eye, presents the appearance of an ordinary star or planet. It would hardly excite remark but for the coma and tail by which it is accompanied. The coma (which is the Latin for 'hair') is a mass of cloudy or vaporous appearance which surrounds the nucleus on all sides. Next to the nucleus it is so bright as to be hardly distinguishable from it, but it gradually shades off in every direction. Nucleus and coma combined present the appearance of a star, more or less bright, shining`