INDUSTRIAL PROGRESS DURING THE YEAR 1874. xxxvii 



of mention the self-registering upsetting thermometer of Ne- 

 gretti & Zambra. Wild, of St. Petersburg, demonstrates that 

 his self-registering balance barometer gives results as accu- 

 rate as the eye observations of any but the most expert ob- 

 servers. Of general works on meteorology, that of Lorenz 

 and Roth is worthy of mention, since it pays special atten- 

 tion to the connection of agriculture and forestry with me- 

 teorology. The investigations of Baranetzky into the pe- 

 riodical flow of sap in trees, as dependent upon atmospheric 

 changes, should be mentioned in this connection. 



Of numerous scientific balloon voyages, we can here enu- 

 merate only those of King and Holden in the United States, 

 of Tissandier in France, and of Brunelle in Russia. The 

 French Association has, by an especial appropriation of mon- 

 ey, stimulated similar voyages. 



Helmholtz gives a calculation which does not promise well 

 for aerial voyages to Europe. He shows that in order to give 

 a balloon a velocity of l&J miles per hour, it would require 

 live per cent, of the power necessary to propel a large ocean 

 steamer 13 miles an hour; but the volume of the balloon 

 would have to be forty-two times the displacement of the 

 steamer. 



Symons has begun the publication in The Colonies of a 

 monthly weather review for the English dominions. The 

 publication of the "Atlas meteorologique" for France, and 

 of the "Atlas generaux," has been resumed. 



PHYSICS. 



In Molecular Science, Professor F. W. Clarke shows that 

 the specific heats of chemical compounds apparently vary 

 with their boiling-points and temperatures. The researches 

 of Plateau on the phenomena of thin films, and those of Van 

 der Walls on the continuity of gases and liquids, have open- 

 ed the way for a satisfactory explanation of many molecu- 

 lar phenomena ; and Maxwell, commenting on the latter work, 

 takes occasion to demonstrate the highly interesting theo- 

 rem " that the molecules of gases attract each other at a 

 certain small distance, but repel each other when they are 

 brought still nearer together, as, for instance, when compress- 

 ed into the liquid state." 



Thurston, of Hoboken, announces that the strength of iron 



