412 SCIENTIFIC EECORD FOR 1882. 



■would take place only by radiation, would be exceedingly slow. {Nature, 

 January, 1881, xxiii, pp. 235 and 237.) 



C. I. McNally, in reference to the heat indicated by thermometers 

 wrapped in hygroscopic coverings and breathed upon by the warm moist 

 breath, writes : " That the effects of friction and comjiression of air are so 

 slight that they may be disregarded, has been proved, and the rise has 

 been clearly traced to absorption of aqueous vapor. It has yet to be 

 determined how much of this heat may be accounted for by the reduc- 

 tion of aqueous vapor to the fluid state and how much by capillary 

 action and absorption of water, with or without chemical union, and its 

 reduction to the solid state, all of which may be included in hygroscopic 

 action. This determination would involve some intricate investigations 

 which some scientific specialist may find leisure to undertake. That 

 more than simple vapor condensation is concerned in the production of 

 hygroscopic heat is shown by the rise of temperature on adding water 

 to a non-saturated hygroscopic substance." {JSTature, January 13, 1881, 

 XXIII, p. 244.) 



Amagat having repeated his experiments on the elasticity of rarefied 

 gases, asserts that they still follow the law of Mariotte even down to the 

 lowest attainable pressure. (The .01 of an inch was his lowest.) {Na- 

 ture, XXVI, p. 384.) 



Maxwell's theory of the viscosity of gases has been elaborately in- 

 vestigated by W. Crookes, who by the x)erfection of his vacua has been 

 able to fully corroborate Maxwell's views, according to whom the vis- 

 cosity should be independent of the temperature. {Nature, xxiii, p. 420.) 



Stevenson states that as a first result of his observations on the law 

 of wind velocities at different heights he finds that the curves traced 

 out by the velocities in relation to the heights were most nearly repre- 

 sented by the formula Y = v V{II + 72) 4- {h + 72), where H and h 

 represent respectively the heights in feet of the high and low level 

 stations above the ground, and V and v the respective velocities at those 

 levels. 



He has since then been making observations with the view of ascer- 

 taining the relative resistance of land and water to the aerial cur- 

 rents. These observations are very far from being complete, but the 

 following results in the mean time may be interesting : 



Sand. Water. 

 6-inch waves, 12.8 : 13. 8 miles per hour = l: 1.08 

 6-inch waves, 13.65 : 14. 375 miles per hour = 1 : 1.06 

 3-inch waves, 7.96: 9. 19 miles per hour = 1 : 1.155 



Grass. Water. 

 9-inch waves, 8. 4 : 10. 7 miles per hour = 1:1. 274 

 3-inch waves, 10. 13 : 14. 75 miles per hour = 1:1. 456 



The velocities given are the means of observations taken every five 

 minutes for about an hour. 



