Mechanical Science. 177 



2. NEW THEORY OP CAPILLARY ACTION. 



M. Poisson has published, as a paper, the first part of a work 

 which will shortly appear, and in which he gives his views of 

 capillary attraction. After viewing what had been done before, he 

 arrives at the conclusion that the phenomena of capillarity are due 

 to molecular action, modified not only by the curvature of the sur- 

 faces, as Laplace has said, but also by the particular state of the 

 liquids at their extremities due to the deficiency on the exterior of 

 that molecular attraction which exists in the interior *. 



3. ON THE APPLICABLE FORCE EXERTED BY A HoRSE. 



M. D'Aubuisson has examined the useful force of a horse by refer- 

 ence to the effects produced at the Freyberg mines, where the ores 

 are raised by this animal power. The horses belong to the neigh- 

 bouring countrypeople, and are occupied for eight hours in the day; 

 they are small for draught horses, but in excellent condition. 



The power of a horse he distinguishes into useful (or applicable) 

 effect, and dynamic effect : the latter being the total force exerted by 

 the animal, and the former that force minus what is consumed by 

 the resistance and friction of the machine, vis inertia, &c. &c. The 

 useful effect is that which it was his object to estimate, and he 

 found it to equal forty kilogrammes raised one metre (or 2.21bs. 

 raised 39 . 4 inches) in a second ; this being understood of a good 

 ordinary horse working for eight hours, in two portions of four 

 hours each, and in machines of simple construction and properly 

 arranged. From some experiments, &c., of M. Hachette, the dynamic 

 effect would appear to be about sixty kilogrammes raised to the same 

 height in the same time f. 



4. BEVAN ON THE RELATIVE HARDNESS OF ROAD MATERIALS. 



Mr. Bevari has sent to the Philosophical Magazine a table contain- 

 ing the results of experiments made in 1825, principally upon the 

 hardness of road materials, or their power of resisting the per- 

 cussion of a given weight of cast-iron falling a few inches upon the 

 several specimens broken to the ordinary size, and resting upon 

 stone or iron. Supposing the weather to have no action, the table 

 would express nearly the relative value of the materials, for the 

 purpose of supporting the wear of a road; and, therefore, those 

 which resist the action of frost and weather, and have the highest 

 numbers, are most valuable. 



Mount Sorrel sienite 100 



White marble 37. 31 



Chert pebble, used much in Mid- 1 04 07 52 56 55 65 



Annales de Chiraie, xlyi, 61. f Annales des Mines, 1830, p. 145. 

 VOL. II. Ava, 1831. N 



