430 



THE POPULAR SCIENCE MONTHLY. 



place3 and tracts of land within the Com- 

 monwealth. The property thus acquired, 

 which can not, with its appurtenances, ex- 

 ceed two million dollars in aggregate value, 

 is exempt from taxation, unless it is held 

 longer than two years without being opened 

 to the public. While the corporation enjoys 

 these privileges, it is forbidden to own any 

 capital stock or to make any division of 

 property or income among its members, or 

 any dividends. Mr. George F. Hoar has 

 been chosen President of the Board. The 

 trustees received last year several recommen- 

 dations or offers of property as coming within 

 the category of the purposes for which they 

 are acting, and have considered the expe- 

 diency of purchasing them ; and Mr. J. B. 

 Harrison, their agent, has made an inspec- 

 tion of the sea-coast towns of the State, with 

 a view to the provision of public access to 

 the beach and the establishment of sea- 

 shore parks. The establishment of the 

 board will enable the admirers of the 

 scenery or history of any spot in the State 

 to make that spot a reservation and to pro- 

 vide for its perpetual care, and will enable 

 the proprietors of pleasure resorts and the 

 people of communities which make money 

 from the attractiveness of fine scenery to 

 insure the perpetuation of such attractions 

 and of their profits. Similar provisions 

 should be made in all the States. 



Characteristics of Star Spectra. The 



general conclusion derived from the study of 

 the spectra of the stars, says Prof. E. Picker- 

 ing, in his account of the Henry Draper Me- 

 morial, is the marked similarity in constitu- 

 tion of different stars. A large part of them 

 the stars of the " first type " have a spec- 

 trum which at first sight seems to be continu- 

 ous, except that it is traversed by broad dark 

 bands, due to hydrogen. Closer inspection 

 shows that the K-line is also present as a fine 

 dark line. If the dispersion is large and the 

 definition good, many more dark lines are 

 visible. These lines may be divided into two 

 classes: First, those which predominate in 

 many stars in the milky way, especially in 

 the constellation of Orion ; and, second, those 

 present in the solar spectrum. Nearly all the 

 brighter stars may be arranged in a sequence, 

 beginning with those in Orion, in which the 

 auxiliary lines are nearly as intense as those 



due to hydrogen. Other stars may be found 

 in which these lines successively become 

 fainter and fainter, till they have nearly dis- 

 appeared. The more marked solar lines then 

 appear, become stronger and stronger, and 

 the hydrogen lines fainter, till they gradually 

 merge into a spectrum apparently identical 

 with that of the sun. Continuing the se- 

 quence, the spectra pass gradually into those 

 of the third type. Certain bands become 

 more marked, and the spectra of the third 

 type may be divided into four classes, in the 

 fourth of which the hydrogen lines are bright 

 instead of dark. This spectrum appears to 

 be characteristic of the variable stars of long 

 period when near their maximum. It has led 

 to the detection of several new variable 

 stars, and has been confirmed in many of the 

 known variables. Slight peculiarities are 

 noticed in the spectra of many stars, but 

 these deviations are not sufficient to affect 

 the general law. Stars of the fourth type, 

 whose spectra appear to be identical with 

 the spectrum of carbon, are not included in 

 this classification. Other stars, whose spec- 

 tra consist mainly of bright lines, like those 

 of the planetary nebula?, may be included 

 with them in a fifth class. 



The Reason of the Slave Trade. A Mos- 

 lem view of the slave trade is presented in 

 the Saturday Review not to excuse the traf- 

 fic, but to show why it is carried on. The 

 slaves are mostly children, " black, uncomely, 

 and unpromising." They are not sought 

 for the harem, in the conventional sense 

 of that word. "The truth is, that certain 

 conditions of domestic life among civilized 

 Moslems exact a supply of slaves without re- 

 gard to beauty or even to physical strength. 

 The interruption of that supply has caused 

 as much dismay and confusion as a law to for- 

 bid the employment of unmarried girls for 

 household service might effect in England. 

 It would be found at once that there were 

 not matrons or widows enough to do the 

 work, that few of them would undertake it, 

 and fewer still were competent. Such a law 

 would be evaded at every peril. No class of 

 women in a Moslem community has the tra- 

 dition of domestic service, as it may be 

 called. Very commonly a free girl was 

 taken into the household of some matron 

 as a child, and there brought up ; but she 



