436 



8CIENCE. 



[Vol. L, No. 15. 



lake, with its briglit, sparkling waters, free from ma- 

 rine vegetation of any sort. 



Mr. Greene also says (p. 76), " The evidence of trav- 

 ellers does not, however, support the suggestion that 

 the Red Sea i< remarkable for an excessive supply of 

 seaweed." From Ehrenberg, ' Die koralleubiiiike,' 

 1832, to the last and best authority on the Red Sea 

 (Klunziger, Upper Egypt, 1878, pp. 34.5-376), we are 

 assured of the direct contrary of Mr. Greene's asser- 

 tion. "A celebrated plant is the shora (Avicennia 



officinalis), which forms large, dense groves in the sea, 

 these being laid bare only at very low ebb. . . . The 

 sea-grass meadows {gisua of the Arabs), which we have 

 already often mentioned, and which are met with 

 partly in depressions in the surface of the reef, partly 

 on the bottom of the sea (especially in harbors), afford 

 conceahnent to a special class of fishes, many of which 

 are distinguished by possessing a green color." — 

 {Klunziger, pp. 240, Slo.) H. o. [918 



INTELLiaENCE FROM AMEBIQAN SOIENTIFIO STATIONS. 



PUBLIC AND PRIVATE INSTITUTIONS. 

 Boston society of natural history. 



Tlie collection of minerah. — The society has just 

 finished the arrangement of its collection of minerals 

 with the express purpose of offering it as an illustra- 

 tion of the mode of arrangement to be adopted 

 throughout their museum. The curator's report, 

 shortly to be printed, has a detailed account of the col- 

 lection, from which we give the following account: — 



The exhibition is divided into three parts: I. Com- 

 parative mineralogy; II. Synopsis of classification; 

 III. Systematic collection. 



I. Under the head of comparative mineralogy, the 

 following topics are treated by means of series of 

 specimens: 1°. Composition and chemical relations 

 of minerals; 2°. Form and structure of minerals; 

 crystallography ; 3°. Physical properties of minerals. 



1°. Under the first liead, such subdivisions as the 

 variation of minerals in composition are dealt with 

 in the cases by the exhibition of several selected 

 series, — (a) variations due to original mixtures; 

 {b) variations due to decomposition and alteration; 

 (c) variations due to chemical substitution. The 

 first (a) of these sub-topics, for example, is ex- 

 hibited in a series of seven minerals. Three of these 

 are varieties of amphibole, and display the distinct 

 colors and aspect due to changes in the chemical 

 composition of the varieties. The second (h) is 

 shown by five minerals, among which are orthoclase 

 and wernerite, — quite distinct substances, but which 

 are undergoing reduction by decomposition to the 

 same mineral, kaolinite. In the third (o) only one 

 substance, phyrrhotite, and its elements, sulphur and 

 iron (which are placed together upon one tablet), is 

 set apart for the exposition of the differences which 

 may exist between the elementary constituents of a 

 mineral, and the compounds resulting from their 

 union. 



The relations of water in the composition of min- 

 erals is dealt with in a series running from a strictly 

 anhydrous hematite to natron (hydr. carb. sodium), 

 having 55 per cent of water. There are twelve 

 specimens in this series, and behind each specimen 

 a tube exhibits the relative proportion of water. 



2°. Form and structure presented no very serious 

 difficulties beyond the need of finding persons capa- 

 , ble of making the special models which were re- 

 quired. This was satisfactorily accomplished after 

 some delay. 



3°. As examples of the methods pursued in illus- 

 trating the physical properties of minerals, we can 

 use the following: — 



(a) The density series, showing the range of min- 

 erals in specific gravity. This series consists of 

 twenty-seven minerals, including gold, which is 

 iwenty-oue times heavier than water, and petroleum. 



which is lighter than that standard liquid. This 

 gradation is made apparent to the eye by means of 

 glass tubes containing equal weights of each of the 

 substances, reduced in the case of solids to a fine 

 powder. Thus gold, with specific gravity 19.5, the 

 heaviest substance, has necessarily the shortest, and 

 petroleum, with specific gravity .75, the longest, tube; 

 and the intermediate tubes show the gradations be- 

 tween these. Thus a series is formed which exhibits 

 clearly that the volume of minerals is inversely pro- 

 jjortional to their specific gravity or weight. 



There are a number of series showing the relations 

 of minerals to light, among which we may select, by 

 way of illustration, that of the color test, or streak, 

 of minerals. 



(h) Streak series: lustre metallic, and color mainly 

 essential. This label stands at the head of nine 

 specimens, each mounted upon the same block, with 

 a piece of novaculite of uniform size, such as is used 

 to try the streak of minerals, partly covered with a 

 band of the powdered mineral. 



(c.) Streak series: lustre non-metallic, and color 

 non-essential except when white. This label is at 

 the head of a precisely similar series, but consisting 

 of eighteen minerals with their accompanying stones, 

 exliibiting the great contrast between the color of 

 minerals themselves and of their streaks upon the 

 white surfaces of the novaculite. 



(d) There are also series of specimens showing the 

 principal minerals which exhibit electrical properties 

 either in their natural conditions, or only when acted 

 upon by friction or heat. 



(e) Even the taste, touch, and odor of minerals are 

 illustrated by similar series. Though persons cannot 

 imagine how a rare mineral tastes, feels, or smells 

 simply from the sight of it, they all know some of 

 the commoner minerals of the same series which are 

 placed on exhibition. With the guidance of the col- 

 lection, they can also more easily duplicate the speci- 

 mens, and understand their relations. 



II. In the synoptical collection, the more important 

 and abundant elements are here repeated, and each 

 shelf is devoted to one of the grand divisions of the 

 mineral compounds. Each division of minerals is 

 represented by its most characteristic species ; and the 

 subdivisions of the anhydrous and hydrous groups 

 are indicated on the labels, wherever these occur. 



III. The systematic collection begins with the na- 

 tive elements, which occupy one wall-case next to 

 the synoptical collection. This is followed by the 

 compounds. These fill the wall-cases on the remain- 

 ing sides of the room; and here are exhibited the dif- 

 ferent species of minerals arranged in their propei' 

 order as classified by Professor Dana, with some 

 slight changes in the succession of the larger divis- 

 ions. 



Models of the i)rincipal or most characteristic crys- 



