PHYSICS OF THE GLOBE. 161 



in a Channel." A few notes are added by the translator, 

 highly appreciative of Humphrey's and Abbot's work on 

 the Mississippi. 



The action of frictional resistance and loss of energy 

 upon water when flowing at various velocities through a 

 nozzle with a converging entrance and diverging outlet has 

 been carefully treated experimentally by James Brownlee, 

 whose memoir thereon is published in Yol. XIX. of the Trans- 

 actions of the Institute of Engineers and Ship-builders in 

 Scotland; following this paper, Mr. R. D. Napier, Professor J. 

 Thomson, and others gave some valuable theoretical exposi- 

 tions of the subject. The same volume contains a careful 

 paper by Mansel, in which are deduced several propositions 

 on the motion of steam-vessels. 



P. D. Heen, in the Brussels Bulletin, 1878, p. 798, commu- 

 nicates an investigation into the laws of the fluidity of liq- 

 uids. He defines the coefficient of fluidity as the relative 

 time required for the molecules to be displaced or to slide 

 over each other to an equal distance in different fluids. He 

 determines this coefficient experimentally for numerous fluids 

 and saline solutions, and applies the results to determining 

 the velocity of flow of the liquids through small apertures. 



The resistance of the atmosphere to the oscillations of the 

 torsion pendulum has been investigated by Cornu and Bailie 

 as one of the preliminaries to their proposed accurate meas- 

 urement of the earth's density. They find this resistance 

 appreciable, and that in consequence of its existence the am- 

 plitude of the successive vibrations diminishes in geometrical 

 progression, while the times of the elongations diminish in an 

 arithmetical progression. It is hence inferred that the re- 

 sistance of the air is proportional to the first power of the 

 angular velocity of the balance. 



Mr. David Trowbridge, of Waterburgh, N". Y., publishes 

 a paper on the atmospheres of the sun and planets, in 

 which he takes account of the temperatures of the sur- 

 faces of the planets and various modifying circumstances, 

 and shows that if the earth were 490 warmer than it now 

 is, the height of its atmosphere would be more than doubled. 

 He shows that Jupiter's atmosphere at his surface is either 

 very dense or else the temperature at the surface is greater 

 than 1000 Fahr. The height of the barometer at the sur- 



