74 Intelligence and Miscellaneous Articles. 



Hence T is proportional neither to A nor to X 2 . — Exner's Reper- 

 torium der Physik, xxvi. p. 102 (1890) ; Beiblatter der Physik, xiv. 

 p. 938. 



ON THE CONDENSATION OF AQUEOUS VAPOUR IN CAPILLARY 

 SPACES. BY G. VAN DER MENSBRUGGHE. 



The author propounds the task of furnishing an exact experi- 

 mental proof of Thomson's theory, that the maximum pressure of 

 aqueous vapour for a given temperature is smaller for a concave 

 surface than for a plane one, and continually decreases with 

 increasing concavity. In the first part of the present research a 

 number of facts are collected which serve as examples for the 

 condensation of aqueous vapour in capillary spaces. Mention is 

 made of the microscopic capillary slits in organic hygroscopic 

 structures, the deposition of ice-flowers on the dusty parts of our 

 window-panes, the phenomenon that particles of iron rust most 

 when they appear protected by materials, such as cloths, dry wood, 

 and the like, w T hich are in contact with them. 



In reference also to Aitken's experiments on the fog-producing 

 action of suspended particles of dust, the author urges as the ex- 

 planation the irregular shape and the ultra-capillary cracks of the 

 individual particles. The author observes incidentally, that the 

 rapid rotting of fabrics, such as tulle, w T hich are often coated with 

 aqueous vapour even in air which is far from its point of satura- 

 tion, may be explained by thermoelectric currents which are 

 formed on moistening and on drying {Bull. Ac. Belg. [2] vol. xli. 

 p. 769, 1876). The durability of the clothing with which Egyptian 

 mummies are wrapped depends on the filling of the capillary cracks 

 with wax. The author strongly recommends that for the preser- 

 vation of oil-paintings they should be varnished on the back. — Bull. 

 Ac. Belg. [3] vol. xix. p. 101 (1890) ; Beiblatter der Physik, No. 11, 

 1890. 



ON ELECTRICAL CONVECTION. BY A. RIGHI. 



In this note the author describes new experiments, which taken 

 in conjunction with those he has previously published appear 

 to him to establish : — 



That in all cases in which there is an escape of electricity either 

 by a point, or by an incandescent body, or by a metal exposed to 

 ultra-violet radiations, the phenomenon is due to convection ; and 

 that the particles in movement follow sensibly the lines of force of 

 the field in which they move. In more or less rarefied air the 

 trajectories seem to diverge more and more from the lines 

 of force; and in the case of an extreme degree of rarefaction 

 they should become almost rectilinear, as appears to be the case with 

 the particles of radiant matter in Crookes's tubes. 



The author proposes to make experiments to see if this gradual 



