THE PROGRESS' OF SCIENCE. 



56; 



and an address by Professor J. II. 

 Poynting on 'Radiation in the solar 

 system.' A number of papers were 

 presented to the section l>y foreign 

 visitors including two by Professor 

 Wood, of the Johns Hopkins Univer- 

 sity, one describing some recenl im- 

 provements in the diffraction process of 

 color photography and another on t lie 

 anomalous dispersion of sodium vapor. 

 Section A includes mathematics and 

 astronomy as well as physics. Among 

 the papers was one by Sir David Gill, 

 director of the observatory at the Cape 

 of Good Hope, entitled " Problems of 

 Astronomy.* which discussed some of 

 the questions in practical astronomy 

 now pressing for solution. 



Before the Chemical Section Sir 

 James Dewar gave an address on very 

 low temperature phenomena with in- 

 teresting demonstrations. He showed 

 by a series of beautiful vacuum-tube 

 experiments the behavior of nitrogen, 

 oxygen, hydrogen and argon when sub- 

 mitted in contact with charcoal to the 

 cooling influence of liquid air. The 

 nitrogen tube exhibited the usual violet 

 color when the spark passed through it, 

 but as soon as the charcoal was im- 

 mersed in the liquid air the tube 

 passed through various stages of at- 

 tenuated brilliancy until ultimately 

 the vacuum became so high that the 

 current could scarcely overcome the 

 resistance. When the liquid air was 

 removed the changes were passed 

 through in the reverse order. Oxygen 

 passed through a similar series of 

 changes, but in the case of hydrogen 

 the absorptive power of the charcoal 

 at the temperature of liquid air was 

 not great enough to render the tube 

 non-conductive. Lord Kelvin, in pro- 

 posing a vote of thanks to Professor 

 Dewar, said that he was filled with ex- 

 pectation as to the condition of things 

 that would be disclosed at a tempera- 

 ture of 5° absolute, where there would 

 be 110 motion. What would become 

 of electric conductivity, of magnetism, 

 of thermal conductivitv? He wished 



Sir .lames would continue his electro- 

 conduct ivity experiments and bring 

 him copper highly conductive at 8° 

 but as great an insulator as glass 

 at one or two or three dcrees. 

 sir William Ramsay, speaking on the 

 changes produced by the |S-rays, said 

 that he had obtained 105 milligrams 

 of radium bromide, which, being too 

 precious to risk in one vessel, were 

 divided amongst three bulbs. These 

 bulbs were placed in glass vessels, and 

 were each provided with a tube to take 

 away emanations. The vessels were 

 colorless to start with, and were some 

 of potash and some of soda glass, but 

 in course of time the former became 

 brown and the latter violet in color. 

 The glass, too, became radio-active, but 

 this property was removed by washing 

 with water, although the color re- 

 mained. When a solution of radium 

 bromide was evaporated an invisible 

 residue was left which was radio-active 

 and dissolved to a radio-active solution. 

 Radium formed chloride, sulphide, 

 hydroxide and sulphate similar to lead, 

 except that they were radio-active. 

 The radium emanations rendered silver 

 and platinum as well as glass radio- 

 active. Professor W. O. Atwater, of 

 Wesleyan University, presented two 

 papers, one on the agricultural experi- 

 mental work in the Smithsonian In- 

 stitution and one on the experiments 

 in nutrition carried out under his direc- 

 tion. 



Mr. Aubrey Strahan's presidential 

 address before the geological section 

 was on earth movements, and this was 

 taken as a subject for special discus- 

 sion. In opening it Mr. Straham said 

 that the subject proposed for discussion 

 was the nature and origin of those move- 

 ments of the earth's crust which have 

 manifested themselves in the factoring, 

 overthrusting and folding of strata. 

 These movements have been in opera- 

 tion from the earliest to the latest 

 geological periods; and, though they 

 have been intermittent so far as any- 

 one region is concerned, there is reason 

 to believe that thev have been more or 



