34 + 



SCIENCE. 



[Vol. XVIII. No. 463: 



taneousTj' with the luminous clouds, a star of the first mag- 

 nitude, Capella, and a star of the same constellation, of the 

 second magnitude, ft Aurigse. 



The brighter of the two stars, which is characteristic of 

 summer nights, in the northern horizon, sets towards the end 

 of June soon after eleven, and towards the middle of July 

 before ten, on account of the northerly direction of the 

 meridian, and, in North Germany, at a distance from the 

 horizon of ten to twelve diameters of the full moon. At 

 almost as great a distance from this bright star, and at a not 

 very different distance from the horizon, the second magni- 

 tude star follows towards the west. 



By estimating the distances and directions of these two 

 stars, an excellent means is afforded of determining the out- 

 lines of a group of luminous clouds. It is only necessary to 

 determine how great the distance of a certain part of the 

 outline of the cloud group is from one or the other star, and 

 in what direction this line lies with regard to one or the 

 other star, or how far the line in question is above or below 

 the prolongation of the connecting line of ttie two stars. A 

 simple drawing of the course of the outlines and their situa- 

 tion with regard to the two stars is useful, even when it 

 cannot be completed on the spot but must be Qnished from 

 memory. The time at which the drawing was made should 

 be noted within one half-minute. 



If the group of clouds should be so far from the above- 

 mentioned two stars as to make the determinations inexact, 

 it is advisable to determine the outlines of the clouds for a 

 certain time in the following way. Take up a position from 

 which the outlines of houses, trees, etc., can be seen close to 

 the position of the clouds, and fix thus the relative position 

 of these earthly objects to the position of the clouds by a 

 simple drawing, describing the spot from which the observa- 

 tion is made in such a manner that the place occupied by the 

 head of the observer can be found again. The lines drawn 

 from the position of the observer to the outlines of the earthly 

 objects, and the resulting localization of the outline of the 

 clouds in the heavens can then be determined at once by 

 means of simple instruments for measuring angles, or on suc- 

 ceeding nights by the aid of a good star chart. 



It is necessary to verify the exact point of time of these 

 observations by comparison of the watch used with the time 

 at a telegraph office, and correction of any errors should be 

 made to the fraction of a minute. 



In communicating these observations, the exact place at 

 which they have been made must be accurately described. 



Should a complete observation be impossible, owing to the 

 time during which the luminous clouds are visible being loo 

 short for careful measurements and drawings or to any 

 other cause, the observer should nevertheless communicate 

 briefly to the Society of Friends of Astronomy and Cosmic 

 Physics that he has seen what he believes from the foregoina: 

 considerations to be luminous clouds from a certain place, in 

 a certain direction in the heavens, and within a certain 

 quarter hour. 



The peculiar movements hitherto observed of the clouds in 

 question lead to the suggestion that perhaps a period con- 

 sisting of several days exists, within which one and the same 

 group of clouds is visible at the same hour from the same 

 place, other conditions of the beavens being favorable. Every 

 communication as to these phenomena will be valuable in 

 the decision of this important point, which it has hitherto 

 been impossible to settle, owing to the uncertainty of the 

 ■weather and the fewness of the observers. 



Those co-operating in our branch of research wbo are in 



possession of astronomical, photographic, or other physical 

 apparatus, will of course be able to give more exact details 

 as to place, movement, and continuation of the luminous 

 clouds. 



Suggestions for these observations cannot be given so 

 briefly and simply; but for the sake of full and complete 

 agreement between different observers, especially as to the 

 point of time selected for talring photographs and measure- 

 ments, members of the Society of Astronomy and Cosniie 

 Physics are invited to communicate with O. Jesse, Steglitz 

 bei Berlin, Albrechtsstrasse 30. This course would also be 

 advisable in the close optical examination of the clouds with 

 regard to the peculiar changes in strength of light and the- 

 degree and kind of self-luminosity which they perhaps senJ 

 out together with the reflected sunlight. 



In the night from June 25-26 of this year the summer re- 

 appearance of the luminous clouds was observed very brightly 

 from Berlin and the neighborhood. 



More detailed particulars on the wliole subject of inquiry- 

 are contained in a small paper by W. Foerster, which has- 

 been sent to all the members of the Society of Friends of 

 Astronomy and Cosmic Physics. 



LETTERS TO THE EDITOR. 



#*« Correspondents are requested to be as brief as possible. The writer's narne- 

 ig in all cases required as proof of good faith. 



On request in advance, one hundred copies of the number co^itaining hi^ 

 communication mill "e furni.ihed free to any correspondent. 



The editor will be glad to publish any queries consonant with the characUr 

 of the journal. 



A Bowlder of Copper and Glacial Striae in Central Missouri 



A FEW weeks ago there was found near this place a small bowl- 

 der, or nugget, of copper, weighing twenty-three pounds. It is; 

 eleven inches long, six inches wide, and three inches thick at^ 

 thickest part. It is almost entirely pure copper, but ^^•ith a thin 

 crust of the green carbonate all over it except at one end, where 

 there is a slight depression, two inches wide, in which there is a 

 thicker coat — somewhat crystalline — of the blue carbonate. In 

 some crevices in it I found fragments of a coarse red sandstone. 



This is a region of impure limestone and shale, of the coal 

 measures, with no trace of copper. But all over the surface of 

 the country in this vicinity pebbles and small bowlders (some- 

 times two or three feet thick) of granite, quaitzite, etc., are 

 found. 



In at least one locality near here there are glacial(?) stri» upon 

 the surface rocks. These are on the top of a bluff on the Missotiri 

 River and about twelve miles south-west of the place where the 

 copper was found. The top of this bluff is at least a hundred and 

 fifty feet above the present level of the river. Its upper layer of 

 rock is of Burlington limestone, which is polished and much 

 marked with striae. These striae are north and south in direction 

 — nearly parallel with the river at that point. 



Taking all these things together, I think my piece of copper is 

 from the Lake Superior region and was brought here by a glacier, 

 A geologist of note, to whom I reported the find, says, " It is un- 

 doubtedly of glacial origin, and probably from Michigan." 



While thoroughly satisfied that this piece of copper is of glacial 

 origin, I am not so decided in the opinion that the striK referred 

 to were made by a glacier rather than by floating ice for the fol- 

 lowing reasons : 



The place where the striae are found is at the summit of an an- 

 ticline which can be plainly traced in the exposed edges of the 

 bluffs for several miles. Standing on the summit of this anti- 

 cline, and looking across the river, you can see, abaut two miles 

 distant, the continuation of the same anticlinal ridge. This also- 

 presents a bluff towards the river. Between the two bluffs is the 

 flat bottom land along the river and the river itself. Now it 

 seems likely that this anticline was lifted up late in time, and may 

 liaie temporarily dammed or obstmcted the flow of the river — 

 then much larger than now. Or an ice gorge in the river at this 



