April 29, 1898.1 



SCIENCE. 



mi 



Since Mr. Horuiman's collection was opened to 

 the public, seven years ago, more than 455,000 

 people have visited it in its temporary home. 



At a meeting of the Trades League of Phil- 

 adelphia on April 14th the following resolu- 

 tions were adopted : 



Whereas, There is at the present time no general 

 system of sanitation and disiutection throughout the 

 United States, guided and controlled by one general 

 head and working in harmony with local and State 

 Boards of Health ; and 



Whereas, The presence of an epidemic of contagious 

 diseases in any part of the country without such gen- 

 eral system of control breeds fear and panic, from a 

 lack of confidence in the ability of the local Board of 

 Health to control the epidemic within a contracted 

 radius of territory ; and 



Whereas, Localities within hundreds of miles of 

 the infected district quarantine against it and other 

 places near it, thus resalting in enormous losses to 

 commercial and transportation interests of the coun- 

 try at large ; therefore, be it 



Sesolced, That the Trades League of Philadelphia, 

 an organization of nearly two thousand business 

 firms, earnestly recommend the establishment, by the 

 National Government, of a commission of public 

 health, to be known as the ' National Commission of 

 Public Health,' which shall be a bureau in the Treas- 

 ury Department, and the duties of which shall be to 

 collect and disseminate information with regard to 

 the pre\alence of infectious diseases in this and other 

 countries, to collect and publish vital statistics, to 

 prepare rules and regulations for securing the best 

 sanitary conditions of vessels from foreign ports and 

 for preventing the introduction of infectious diseases 

 into the United States and their spread from one 

 State or Territory or the District of Columbia, and, 

 in general, to make investigations, publish informa- 

 tion and formulate rules with a view to the preserva- 

 tion of the public health. 



Ilesoli:ed, That the Legislative Committee of the 

 Trades League shall give the subject their careful and 

 prompt attention, with' power to act ' as the impor- 

 tance of the subject may demand. 



In a recent lecture at the Royal Institution, 

 London, on some analytical uses of liquid air, 

 Professor Dewar stated, according to the ac- 

 count in the London Times, that low-tempera- 

 ture work has been greatly extended of late, 

 and that both on the Continent and in America 

 there had been a large development in the ap- 

 plications — or projected applications — of liquid 



air. He proceeded to explain the use of this 

 agent for the qualitative separation of the gases 

 composing a mixture, and practically illustrated 

 the method with a sample of the gas given off 

 by the Bath springs, which was thus shown to 

 contain argon, helium and a hydro-carbon that 

 was liquid at ordinary temperatures. Re- 

 ferring to the cessation of chemical action with 

 extreme cold, he said that photographic effects 

 alone persisted, but had lost some 80 per cent, 

 of their intensity. It was a curious fact that the 

 photographic activity of ultra-violet light, 

 though the greatest at ordinary temperatures, 

 suffered most diminution at low ones. In con- 

 clusion the lecturer spoke of the thermal phe- 

 nomena presented by the vacuum jacketed ves- 

 sels, of which he introduced the employment. 

 Pictet after an elaborate investigation concluded 

 that below a certain temperature all substances 

 had practically the same thermal transparency, 

 and that a non-conducting body became as in- 

 effective as a conducting one in shielding the 

 vessel from heat. But Professor Dewar's ex- 

 periments showed that such was not the case, 

 the transference of heat observed by Pictet ap- 

 pearing to be due not so much to the materials 

 themselves as to the air contained in their in- 

 terstices. By lining the annular space between 

 the walls of several similar vacuum vessels with 

 various substances and exhausting them all 

 equally of air, he found large differences in the 

 thermal transparency of the substances, as 

 measured by the rate of evaporation of liquid 

 air contained in the tubes. Moreover, the 

 thermal transparency of some materials dimin- 

 ished at very low temperatures instead of in- 

 creasing, as had been asserted to be the case. 

 Thus, of two vacuum tubes, one simple, the 

 other having powdered carbon in the vacuous 

 space, the latter at low temperature was the 

 more eflBoieut preserver of a liquid air, showing 

 that the carbon diminished the radiation. But 

 when the vacuum was destroyed and warm air 

 admitted into the space, the liquid in the car- 

 bon tube boiled off much more vigorously than 

 that in the simple tube, indicating that at an 

 ordinary temperature carbon allowed more heat 

 to pass than did air. 



One of Dr. Linde's machines for the lique- 

 faction of air, says the London Times, has been 



