382 



POPULAR SCIENCE MONTHLY. 



specimens of uraninite, or pitchblende, 

 one from mines in Cornwall, and the 

 other from Bohemia; as is well kno^vn 

 to readers of the Monthly, only a few 

 decigrams of radium can be separated 

 from a ton of the mineral, and the iso- 

 lation of the element is difficult, owing 

 to its chemical affinities with the 

 metals of the alkaline earths (barium, 

 strontium and calcium). In contrast 

 with the velvety black, massive pitch- 

 blende, are a few decigrams of pure 

 radium bromide, a white salt resem- 

 bling exteriorly common salt. ' Near by 

 is a salt of barium, the crystals of 

 which are rendered luminous when ex- 

 posed to the emanations from a radium 

 compound, even when a pile of copper 

 coins, or a piece of marble more than 

 one inch in thickness, is placed between 

 them. The labels on these specimens 

 duly explain that these emanations 

 also act in the dark on photographic 

 plates, and make the air traversed by 

 them conductive of electricity. 



The exhibition also includes the fol- 

 lowing: A box blackened inside and 

 mounted on a stand, the whole re- 

 sembling somewhat a large photo- 

 graphic camera, especially since the 

 open end of the box is screened with 

 black velvet that might be mistaken 

 for a focusing cloth. On raising this 

 screen the visitor sees at the farther 

 end in letters of light, the word 

 R-A-D-I-U-M. This word has been 

 painted with radium bromide on hexag- 

 onal sulphide of zinc, which becomes 

 luminous when brought near a com- 

 pound of radium. Thus the emission 

 of light by the new element is demon- 

 strated as effectively, though not so 

 strikingly as by Sir William Crookes 

 in his experiments at the conversazione 

 of the Royal Society, when the scintil- 

 lations of radium were rendered visible 

 by means of a blende screen and in- 

 tensified by the use of a lens of mod- 

 erate magnifying power. Residents of 

 London, and visitors to that metropolis, 

 will enjoy forming practical acquaint- 

 ance with radium and witli some of its 



extraordinary properties that may be 

 envied by citizens of America. 



THE FRANKLIN PAPERS IN THE 



LIBRARY OF THE AMERICAN 



PHILOSOPHICAL SOCIETY. 



At the meeting of the American 

 Philosophical Society last spring, Mr. 

 J. G. Rosengarten gave an account 

 of some seventy large folio volumes 

 of Franklin's papers, preserved in the 

 archives of the society. Franklin left 

 all his papers to his grandson, William 

 Temple Franklin, who, after a long in- 

 terval, published in London and in 

 Philadelphia six volumes of Franklin's 

 works. Of course, this represented 

 but a small part of his papers. Those 

 used in the preparation of Temple 

 Franklin's edition are now the prop- 

 erty of the United States, which has 

 never yet printed a calendar of them. 

 Temple Franklin selected from his 

 grandfather's papers those that he 

 thought suitable for publication, and 

 left the rest of them in charge of his 

 friend, Charles Fox, to whom he be- 

 queathed them, and Charles Fox, in 

 turn, after a long lapse of years, pre- 

 sented them to the American Philo- 

 sophical Society, in whose custody they 

 have remained ever since. 



They have been roughly classified, 

 and are bound in a rude and careless 

 way. Under the present efficient 

 librarian. Dr. Hays, a calendar is being 

 made as fast as the limited means at 

 his disposal will permit, and, when 

 it is completed, it is hoped that it 

 will be printed as a useful guide to the 

 miscellaneous matter collected here. 

 Sparks, Hale, Ford, Parton, Fisher and 

 others who have written about Frank- 

 lin have used them, but even the most 

 industrious student may well be ap- 

 palled at the labor required to master 

 all the contents of these bulky volumes 

 representing Franklin's long and many- 

 sided activity. 



He kept copies of most of his own 

 letters and the originals addressed to 

 him, often indorsing on them the heads 



