July 29, 1892.] 



SCIENCE. 



65 



seai'ched for possible causes of their unhealthy condition. 

 The trees in the best condition to examine were those on 

 which the leaves were yet green, but from their general ap- 

 pearance indicated that they had been attacked by the char- 

 acteristic trouble which was shown in a few yellow leaves at 

 the tops. The roots of such trees were found in a perfectly 

 healthy condition for some distance beneath the surface; the 

 bark on the trunks from a distance of from five to fifteen 

 feet from the base was green, full of sap, and apparently 

 healthy; the leaves were almost free from insect attack and 

 disease, in no case was there sufficient attack of this nature 

 to indicate even a slight injury; the bark, however, at a 

 point about two-thirds up from the base of the tree, was 

 found in every case to be infested by Dendroctonus fron- 

 talis in sufficient numbers to kill all the bark for some 

 distance above that point, aud in this bark fully-developed 

 beetles and pupa were found on May 5, thus indicating 

 that the eggs must have been deposited in the bark the pre- 

 vious summer or fall. All of the characteristic dead and 

 dying Pine and Spruce trees examined showed abundant 

 evidence that they had been invaded while yet green by this 

 bark beetle. 



It would seeDi that the turpentine escaping into the bur- 

 rows made by the beetles in the green bark would render the 

 conditions unfavorable for the progress of their work. They 

 have, however, the power of removing it from their burrows, 

 and they manipulate the sticky resinous substance with 

 seemingly as much ease and in a like manner as the crawfish 

 does the clay it piles up around its burrow. Often a half 

 teaspoonful of the turpentine will be found massed about the 

 entrance to the burrows made by the beetle. They push the 

 turpentine out through a hole kept open in the pitchy, ad- 

 hesive mass. I have observed them backing out from the 

 entrance, shoving behind them a quantity of the turpentine, 

 and at the same time they would be completely enveloped in 

 it. 



Trees invaded by these beetles the previous fall may re- 

 main green until spring when they are usually attacked by 

 the large Dendroctonus terebrans, Hylurgops glabratus, and 

 Tomicus calligraphtis, the two former at the base of the 

 tree, the latter in the green bark above. They are in turn 

 followed by numerous other species of bark and timber 

 beetles until the invaded trees may be, as I have found, the 

 hosts of at least twenty-five species of scolytids coming like 

 reinforcements to the aid of D. frontalis to make doubly 

 sure the death of the invaded trees. Later on, these scolytids 

 are followed by insects belonging to other families until a 

 dead or dying tree may be the host of hundreds of species 

 and millions of examples, breeding in and feeding upon every 

 part of the tree from the base to the terminal twigs, render- 

 ing it worthless for lumber within a year after it dies. 



Thus it will be seen that Dendroctonus frontalis may be 

 the primary cause of not only the death of the trees but of 

 their rapid decay. 



West Va. Agricultural Experiment Station, Morgantown, West Va., July 20. 



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 of the journal. 



Auroral Display. 



On Saturday evening, July 16, there was visible, from this local- 

 ity, in the northern heavens, the most brilliant auroral display 

 which I have witnessed since the year 1859. Besides the usual 



exhibition of streamers of various hues, dancing along tlie northern 

 arch like great hanging curtains, there was one most unique 

 feature which I never saw or heard of before. A little after 10 

 o'clock, when the great brilliance of red and pink streams seemed 

 to be dying out, and the northern heavens assuming a pale uni- 

 form hue, there appeared directly overhead a well-defined, nebu- 

 lous arch, spanning the entire vault of heaven from east to west. 

 At first a companion suggested that it was the Milky Way; but a 

 few seconds' observation detected the Milky Way, running nearly 

 at right angles with the arch — the two resembling each other 

 somewhat in width and general appeai'ance, except that the arch 

 was more clearly defined and uniform in shape and outline than 

 the other. In about fifteen minutes it began to fade away and 

 disappear, the eastern portion disappearing first. In a short time 

 there was only a bright strip near the western horizon, which 

 much resembled the tail of a comet; but it, too, soon disappeared, 

 and there were then no traces of the arch to be seen. 



However, in a few minutes it began to reappear, and soon shone 

 out bright and clear as before, — the arch being five to six degrees 

 in width, — the eastern extremity at the horizon being a little south 

 of east, and the other extremity being a little north of west, as if the 

 whole had been drawn by a radius of a circle whose centre was a 

 little east of the north pole. In ten or fifteen minutes this arch 

 also disappeared as before. 



Between the arch and the upper extremities of the gay stream- 

 ers in the north there were several degrees of space lighted up by 

 stars, and without any apparent connection between them. The 

 band or arch seemed wider at the zenith than on either horizon — 

 probably the effect of the greater distance of the horizon points 

 from the position of the observer. The night air was quite cool, 

 and I retired before midnight ; and I have not learned whether or 

 not the arch agam reappeared. T. A. Beeeman. 



Mount Pleasant, la., July 20. 



Magnetic Storm, Aurora, and Sun-Spots. 



A MAGNETIC storm raged here from 10.30 A.M to 4.30 p.m., cen- 

 tral time, on Saturday, July 16, 1892. An electro-magnetic wave 

 reached the general telegraph office of the C. B. & Q. R. R. at 

 10.30 A.M., making it difficult to operate, especially with the 

 quadruplex. The duration of the electric disturbance was six 

 hours ; but the impulses came with varying intensity. The energy 

 always appeared as a wave, beat, or oscillation; and when fully 

 developed in the wires, seemed to set up a counter electro- motive 

 force in opposition to the batteries. The fact that electro-mag- 

 netic energy traverses space in the form of waves, coincides with 

 the now classical experiments of Hertz, who projected these waves 

 not only through space, but brick walls. Perhaps a law like this 

 will be discovered — All modes of energy alternate. 



It is doubtful if a constant pressure exists in nature. In some 

 instances, telegrams have been sent by means of nature's elec- 

 tricity — without batteries. This is merely a prophecy of that 

 time coming when men will appropriate electricity when they want 

 it, as they do light and heat. 



An aurora appeared at 9.40 p.m., and consisted of many pearl- 

 colored columns, at times tinged with red, occupying more than 

 100'^ in azimuth, and all converging near Polaris. 



At 9.45 an apparition unusual in auroral displays was seen. This 

 was a streamer of nearly white light, that, starling in a sharp point 

 almost on the horizon, in the north-west, shot with great velocity 

 north of Arcturus, passed over Corona Borealis, which constella- 

 tion it equalled in diameter, crossed Hercules and Cerberus, and, 

 passing over Altair, descended almost to Mars in the south-east, 

 terminating also in a fine point. 



This majestic sword moved bodily 10" to the south, and. 

 after shivering and pulsating throughout its length three times, 

 vanished, after existing fourteen minutes. The whole aurora 

 lasted forty minutes. On July 9, a large cluster of spots, 

 with two smaller groups and one larger isolated spot, were 

 seen on the sun. All the larger spots had bridges, and on the 

 12th and 13th the tongues across the large one began to curve, 

 which cm-vature rapidly increased on the 14th and loth. On the 

 16th, these jets were arranged nearly in a circle, or had assumed 



