RECENT PROGRESS IJST CHEMISTRY. 525 



of physics and pharmacy, these chemical periodicals issue annually 

 about twenty thousand pages. Bearing these statistics in mind, are 

 we not justified in feeling appalled at the idea of presenting within 

 the compass of an evening's address a review of recent progress in 

 chemistry ? Any attempt to do more than glance at a few salient 

 points is obviously out of the question. " Recent " time will of neces- 

 sity be a somewhat variable quantity, its limits being determined by 

 expediency. We shall also endeavor to bear in mind the fact that we 

 address an audience not exclusively composed of professional chemists. 



Much interest is commonly attached to announcements of new 

 forms of matter an interest out of proportion, perhaps, to the real 

 value of the discoveries. During the last nine years chemists have 

 not failed to sustain this interest, for they have proclaimed no less 

 than thirty-four new elementary bodies. The ambition of these chem- 

 ists, however, has been greater than their accuracy, for of these thirty- 

 four bantlings but five or six have survived the scrutiny of the doctors, 

 two or three are now in precarious health, and the remainder have 

 been cremated without ceremonies. Of the youthful survivors com- 

 paratively little is known ; their character is being severely tested, 

 and their future destiny and utility are yet uncertain. The extreme 

 rarity of the minerals in which the new elements have been detected, 

 the excessively small percentages of the new ingredients, the extraor- 

 dinary difficulties attending their separation from known substances 

 combine to render the investigations laborious, protracted, and costly. 

 From twenty-four hundred kilogrammes of zinc-blende, Lecoq de 

 Boisbaudran, the discoverer of gallium, extracted sixty-two grammes 

 of the precious metal ; compared with this element, therefore, gold is 

 both abundant and cheap. Ytterbium, scandium, samarium, thuli- 

 um, and the rest, will long remain mere chemical curiosities known to 

 but few ; probably the most sanguine will not claim for them a future 

 place among substances of economic value. 



But of far greater importance than the elements themselves is the 

 marvelous delicacy of the means used in detecting and isolating them. 

 When Bunsen and Kirchhoff presented to scientists the instrument 

 which combines the penetration of a telescope with the power of a 

 microscope magnified a hundred-fold, they were enabled to disclose 

 Nature's most hidden secrets. The new elements have been traced to 

 their hiding-places, their differences established, and their subsequent 

 purity demonstrated, chiefly by their emission and absorption spectra. 

 Three years ago, William Crookes, who had already discovered thal- 

 lium by the aid of the spectroscope, announced a novel and remarkable 

 extension of the power of this instrument. Crookes found that many 

 substances, when struck by the molecular discharge from the negative 

 pole in a highly rarefied atmosphere, emit phosphorescent light of 

 varied intensity. Having observed under these conditions a bright 

 citron-colored band or line, he pursued the substance producing it, and, 



