June 2, 1893,] 



SCIENCE. 



303 



altered, the minor axis is least." Miss H. says: "This is equiva- 

 lent to saying that the mean distance of the earth from the sun is 

 a function of the eccentricity of the earth's orbit, . . ." and then 

 she proceeds to find an expression for this mean distance, first 

 from the standpoint of geology, and, second, from a considera- 

 tion of the kinematical element of velocity. The result in the 

 first case is that 



r' (mean distance) = a \/ \ ^^ 



and in ihe second case that 



r' =a \' \ _e2. 



From what is said in introducing the second case it appears as 

 if the kinematical result were only an "as it were" mean dis- 

 tance, and not the actual average of all the different distances. 

 If this were so, this part of the article would scarcely supply an 

 interlinear reading for the passage from Ball, for it seems evident 

 that he means the real average distance and not a virtual aver- 

 age. The geometrical result should give the real average, but 

 does it — I mean does Miss H.'s geometrical result give it? This 

 makes it equal to the semi-axis minor, but that surely cannot be 

 true. Of course, it is quite true. and. as Miss H. says, it is easily 

 shown that 



but she does not show ho«- it is shown that the mean distance 

 = 1 f" TdB. 



As an assumption it does not seem to be convincingly reasonable. 



The assumption made in the kinematical discussion seems 

 much more reasonable. It is that the mean distance is the radius 

 of a circle, in the circumference of vv'hich a point travels with the 

 same areal velocity as that of the earth in its orbit. If the idea 

 of velocity be dropped, we shall get back from kinematics into 

 geometry, and the same assumption will give us for mean dis- 

 tance the radius of a circle whose area is equal to that of the 

 given e lipse. 



Thus TT »•! = TT a 6 



and 



■•• ''0 = V a6 = « (^ 1 — e2- 

 This is the same as Miss H.'s kinematical result, and, like it, 

 agjees with the dynamical result in her equation (4). 



AUCE POETER. 

 Yarmoutla, N.S., May 15. 



A Beautiful Spectacle. 



I GIVE below a description of a phenomenon seen here on the 

 evening of May 9 and wish you or some of your readers could tell 

 me if it is rare or common, and what is the cause or its relation 

 to other phenomena 



On Tuesday evening. May 9, between 9.15 and 9.45 (north lati- 

 tude 44°, west longitude 66°, but time is 60"), we were treated to 

 a curious and beautiful spectacle. Right across the sky from 

 west to east stretched a magnificent arch of luminous radiance. 

 On the west it seemed to spring from a solid mass of black cloud 

 which extended along the whole northwest horizon. Its width 

 was nearly uniform from the western base up beyond the summit, 

 and measured about two degrees. The summit was among the 

 stars of Berenice's Hair, and was 15 to 30 degrees south of the 

 zenith. The eastern branch narrowed as it neared the horizon, 

 and tapered off to a point before quite completing the semi-circle. 

 The color was fairly uniform throughout, and of a grayish or 

 pale-bluish white, some say "yellowish." Except for the cloud- 

 mass in the northwest the sky was beautifully clear, and the 

 brighter stars along each side of the arch seemed to shine out 

 with unusual brilliancy and sparkle. Those covered by the arch 

 were not obscured, but twinkled through it as through a trans- 

 parent veil. To some observers the summit seemed for a time to 

 move very slowly a little farther south, and near the time of 

 breaking: up there were narrow, dark rifts crossing it obliquely; 

 but, on the whole, the entire structure stood remarkably steady, 



without any of the swaying, or shooting, or shimmering, or 

 wavering motion generally seen in auroras. There had been 

 some auroral outbursts about half an hour earlier, and this phe- 

 nomenon was probably connected with them. Whatever it was 

 due to, it was a splendid sight — such a sight as the rings of 

 Saturn must be as seen from the surface of that planet — and it 

 was much admired by all who saw it. It broke up and melted 

 away before 10, and in another quarter of an hour the sky was 

 clouded all over. Alice Porter. 



Yarmouth, N.S., May 13. 



A Fall of Colored Snowr. 



On .Ian 8 1892. between one and five o'clock p.m., there fell 

 about one inch of colored snow throughout the northern half of 

 La Porte County. Ind. 



.Mixed with the snow was a large percentage of mineral and 

 vegetable matter giving the snow a reddish-brown hue. Every 

 flake of snow had a particle of this matter, that served as its 

 nucleus, from which the mass became granular. The mass was 

 moist enough to form a crust within twelve hours. 



At the time it fell there were six inches of clean snow very 

 evenly distributed over the surface, probably not any surface bare 

 within fifty miles of the above-named area. This old snow was 

 quite compact. 



During the next twenty-four hours following the fall of colored 

 snow about four inches of clean snow fell on top of it, and became 

 a crust within a few days, thus embedding the colored snow be- 

 tween two compact strata of ordinary snow, by which it was 

 kept free from contamination for about a month. During that 

 time several persons procured samples of it for examination. 



The meteorological conditions at the time of its fall were : Wind 

 from west-southwest; all clouds moved in same direction. Tem- 

 perature about zero at 8 a.m. Jan. 8, 13 to 3 p.m., rising; 8 p.m., 

 zero. Thermometer stood at zero Jan. 9. At Chicago from 4 

 until 4 30 there was light snow, too light to measure. At Grand 

 Haven, Mich., it snowed almost continuously from Jan. 5 to 10; 

 and on Jan. 8. thermometer fell from 18 to 8 above zero (the 

 co'dest of the season); while at Chicago it went down as low as 5 

 below from 12 above zero. That station reports a high-pressure 

 area for the whole northwest country, weather cold and clear. 

 This area closely followed an area of low-pressure, which was 

 central over Upper Lake Michigan during the morning of Jan. 8, 

 moving rapidly northwestward during the succeeding twenty-four 

 hours, general snow marking its passage. The Chicago observing 

 station records wind from west to northwest Jan. 8-9. 



Having had my attention called to some of these facts by an 

 article in a local newspaper by Honorable G. H. Teeter of Rolling 

 Prairie, Ind.. I began to collect simples, and procured one from 

 that gentleman. I sought to make a survey of the area covered 

 by its fall, but was unable to locate bounds in any direction, 

 although I traced it over an area aS by 45 miles. 



To avoid uncertainty in an analysis of the matter. I drove sev- 

 eral miles into the country with Professor F. M Watters, then 

 science teacher in La Porte High School, to procure samples of it 

 that should not be affected by dust from chimneys and railroads. 

 I made three analyses of it, besides carefully examining it under 

 the microscope, using both low and high powers. Meanwhile. 

 Mr. Teeter procured an analysis by Professor H. A. Huston, 

 chemist of Indiana Agricultural Experiment Station, at Purdue 

 University, Lafayette, lad., as follows: — 



" Loss on ignition (water and other volatile matter) 15.04 



Silica 65.04 



Alumina and oxide of iron 15 50 



Lime 3.19 



Magnesia 1.38 



Phosphoric anhydride .10 



Oxide of titanium and undetermined 15 



Total 100.00 " 



Professor Huston adds: -'The composition of the material is 

 such that one is led to believe it to be of volcanic origin, as it ap- 

 proximates vepy closely to some of the analyses of lava from the 



