;6o 



jCIENCE. 



[V..1. XVI. N;-. 412 



study of the Surface-Markings of the Planets in 1890. 



The progress of astronomy during tbe year 1890 has been note- 

 worthy in many ways. Some of the important particulars will be 

 given briefly in the references that follow. 



The study of the surface-markings of the planets has had a 

 leading place in the work of astronomers giving special attention 

 to observation of this kind. The most startling announcements 

 that have appeared this year are those made by the distinguished 

 Schiaparelli of Milan, Italy, concerning the rotation periods of the 

 planets Mercury and Venus. The first publication of this won- 

 <ierful discovery, that we know of, was made Dec. 8, 1889, in a 

 public address h? Schiaparelli, before the Accademia dei Lincei 

 ■of Rome, in a special sitting, attended by the King and Queen of 

 Italy. 



The discovery was by no means accidental. It was made in the 

 usual way of determining the rotation time of a planet, and that 

 was by observing spots on the surface ; and the conclusion reached 

 is, that the rotation time of the planet Mercury is the same as its 

 period of revolution around the sun, its axis being nearly perpen- 

 dicular to the plane of its orbit. The markings were faint, said 

 to be exceedingly difScult to observe, and Schiaparelli has also 

 found the same thing to be true in regard to ths rotation of the 

 planet Venus. 



M. Perrotin, director of the observatory at Nice, made a series 

 of observations on the markings of the planet Venus for seventy- 

 four days between May and October, for the purpose of testing for 

 himself Schiaparelli's results. His conclusion is, that the rotation 

 time of the planet Venus does not differ from the time of revolu- 

 tion around the sun moie than thirty days, making its time of 

 rotation somewhere between one hundred and ninety-flve and two 

 hundred and twenty-five days. He also finds that the axis of the 

 planet is almost perpendicular to the plane of its orbit. The dis- 

 placement of the white region, observed at the northern edge of 

 the terminator, indicates a difference not to exceed fifteen degrees, 

 ■as was admitted by Schiaparelli. This important work materially 

 strengthens the views of Schiaparelli. 



Coming nearer home in our study of the surface-markings of 

 the planets, it should be mentioned that the change of latitude, 

 or the variation of latitude on the earth's surface, should be men- 

 tioned as a question of much interest in scientific periodicals for 

 the year 1890. Significant and unexplained results are found in 

 the records of some of the oldest observatories in the world that 

 indicate a change in latitude. 



At a meeting some time ago, the International Geodetic Asso- 

 •ciation discussed this important question ; and at another soon to 

 be held, if deemed wise, plans will be made to undertake an ex- 

 tended series of observations by observatories in both hemispheres, 

 for the purpose of determining whether or not the latitude of a 

 place is constant, or a variable quantity. Professor Porro of the 

 Eoyal University of Turin is much interested in pushing this work 

 forward. 



In this country the study of the markings of the planet Mars 

 for the last year received as much, if not more, careful attention 

 • by Professor W. H. Pickering of Harvard College Observatory 

 than by any one else. Although the last opposition was not a 

 iavorable one for the delicate and severe work required of one 

 who can observe the ' ' canal " system of Mars, it gives us pleasure 

 to record what he did. His work was by photography at Mount 

 Wilson, California, and by visual observation at Cambridge, Mass., 

 using the Boyden 13-inch refractor. 



His attention was directed to two points, — the colors exhibited 

 l)y the planet, and the finer detail upon the surface. In regard to 

 surface delineation, he thinks that Green's map gives much the 

 best idea of the appearance of the planet, and the general shape 

 of the details, of any thing yet published; and still his observations 

 at Cambridge give considerable fine detail ndt shown on Green's 

 map, all of which agrees more or less with' that reported by 

 Schiaparelli. Professor Pickering regards the name "canal" as a 

 very unfortunate term by which to designate the strange surface- 

 markings, because there is not the slightest evidence to support 

 the supposition that they are filled with water: on the contrary, 

 such a view is a very improbable one. Though he can see a large 



part of this surface delineation, he is not able to see the markings 

 called "canals" double, as described by Schiaparelli. He de- 

 servedly expressed great admiration for the patient study and the 

 keen eye of the astronomer who could discover details of Mars 

 with an eight-inch telescope, because of the great difBculty of 

 seeing them with larger instruments when their places and char- 

 acters are known. During the present year Schiaparelli has re- 

 viewed his former work on the study of Mars' surface; and a 

 report of the same appears, by Dr. F. Terby of the Academy of 

 Belgium, in the November number of L'Astronomie. This late 

 account of the work of the original discoverer is important, in that 

 it confirms his former results, and adds to them interesting details 

 in regard to the apparent widening of some of the canals and the 

 apparent change of duplicity in the different parts of the same 

 canals at different times. This report will be read with great in- 

 terest, because it strongly confirms Schiaparelli's former views, 

 which have been cautiously entertained by astronomers gen- 

 erally. 



The most interesting work on the detailed study of Jupiter 

 during the past year is by J. E. Keeler of the Lick Observatory. 

 His drawings, made by the aid of the 3a-inch equatorial during 

 the months of July and October, are most excellent specimens of 

 sharp delineation in variety of detail. The fine shading of the 

 belts, the Great Red Spot in distinct outline, with the broken bands 

 veering in latitude as they pass the spot, the round white spots, 

 the oblong dark spots tinged with red at the bottom, and the 

 satellite and its shadow in transit, are some of the very interesting 

 features of Jupiter's surface-markings which Mr. Keeler has put 

 on record in these drawings. The new features about the oval 

 spots are their shape and red color at the base. By other observers 

 they have been spoken of as round, and we do not recall that 

 others have noticed the color which they all show at the bottom. 

 This is doubtless due ,to the superior power of the Lick telescope. 

 Taking into account the fact that Professor Young has seen a veil- 

 ing of the Great Red Spot, — something like a white film over it, 

 if we understand his words, — and the views of Mr. Keeler shown 

 in his drawings, where the dense dark clouds are bent about it as 

 they pass it, and something of the same color as that of the Great 

 Spot seen at the base of the dark oval spots on the other side of 

 Jupiter's equator, it seems as if signs of important changes in the 

 surface character of the giant planet are constantly going on be- 

 fore our eyes from year to year. 



We are sorry that Mr. Keeler's fine drawings have not been 

 published in this country. They have nearly all appeared in for- 

 eign scientific journals. Wm. W. Payne. 



Carieton College Observatory, Dec. 16. 



Snake Hill, N.J , as a Locality for Minerals. 



BEESia told chat there had been some crystals found at Snake 

 Hill, N.J., early in 1888 I started out, accompanied by a young 

 mineralogist, and traversed a road leading across a marsh to the 

 hill, for a distance of five miles. We sought out the quarry where 

 the convicts from Hudson County are educated in the art of blast- 

 ing. It is about a hundred feet high, and overlooks the Hacken- 

 sack River. 



The hill is an ejection of trap, surrounded by sandstone, the 

 rock being used in macadamizing the county roads. We found 

 several veins of minerals running across the quarry. 



The principal minerals which we found and classified are datho- 

 lite in fine glassy crystals ; pectolite in long aggregations of crys- 

 tals, some exceeding three inches in length and in fibrous radia- 

 tions; laumonite in fine, needle-like crystals; prehnite in small 

 balls of a beautiful green color ; natrolite in fine glassy aggrega- 

 tions of fibrous crystals; analcite in excellent trapezohedrons, 

 some of which measured nearly one inch across; apophyllite in 

 fine ti-ansparent square octahedrons, prisms, and tables; gmelinite 

 in excellent aggregations of pink crystals, rhombohedral in form, 

 and modifications of the same, some of which were three-quarters 

 of an inch across ; stilbite in prismatic crystals and acicular ag- 

 gregations of brown and white color; heulandite in brownish 

 rhomboidal crystals; calcite, massive, of white, yellow, and green 

 colors, and dog-tooth crystals of yellow color. There were many 



