164 Proceedings of the British Association. 



object of the machine is to apply to the numerical calculation of 

 definite integrals, a principle first suggested by M. Poncelet for 

 the registration of dynamometrical admeasurements, which has 

 been applied by M. Morin to an instrument called the Compteur, 

 for registering the traction of loaded carriages upon common 

 roads, and during the last year, by a committee of the Associa- 

 tion, to a permanent registration of the work of the steam upon 

 the piston of a steam engine. 



On determining distances by the aid of the Telescope, by 

 Mr. Bowman. The principle of this method was to observe the 

 number of divisions of a graduated staff placed at a distance j 

 and considerable ingenuity is shown in determining the distance 

 by making the necessary corrections on this observed number. 

 The author thinks his method would be more accurate in sur- 

 veying than the actual measurement by the chain, particularly 

 in uneven ground ; and asserts that the error in taking any dis- 

 tance could not exceed the thousandth part of the entire distance ; 

 hence, by dividing the entire distance, even when large, into a 

 number of parts, he conceives that great precision would be at- 

 tained. 



Sir J, Herschel transmitted fifteen specimens of colored photo- 

 graphic copies of engravings and mezzotintos, into the prepara- 

 tion of which no metallic ingredient enters, the whole being 

 tinted with substances of vegetable origin variously prepared. 

 The rays of the spectrum which have eaten away the lights in 

 these photographs, are neither the so-called chemical rays beyond 

 the violet, nor the calorific rays beyond the red. The action is 

 confined almost entirely to the luminous rays, and of these more 

 especially to those rays of the spectrum whose union forms a 

 color supplementary to that of the ground-tint ; a circumstance, 

 which, considering the great command of color which this new 

 variety of the photographic art affords, holds out no slight hope 

 of a solution of the problem of a photographic representation of 

 natural objects in their proper colors. 



(To be concluded in the next numher.) 



