160 Intelligence and Miscellaneous Articles. 



his former communication on the structure of Eozoon, and which led 

 him to infer the Nummuline affinities of that ancient Foraminifer — 

 a determination which has since been confirmed by Dr. Dawson. 

 This " asbestiform layer " was then shown to exhibit in Eozoon a 

 series of remarkable variations, which can be closely paralleled by 

 those which exist in the course of the tubuli in the shells of existing 

 Nummuline Foraminifera, and to be associated with a structure 

 exactly similar to the lacunar spaces intervening between the out- 

 side of the proper walls of the chambers and the intermediate 

 skeleton by which they become overgrown, formerly inferred by the 

 author to exist in Calcarina. 



Dr. Carpenter then combated the opinion advanced by Professor 

 King and Dr. Rowney in the preceding paper, and stated that, even 

 if the remarkable dendritic passages hollowed out in the calcareous 

 layers, and the arrangements of the minerals in the Eozoic lime- 

 stone, could be accounted for by inorganic agencies, there still re- 

 mains the Nummuline structure of the chamber-walls, to which, the 

 author asserts, no parallel can be shown in any undoubted mineral 

 product. 



In conclusion the author stated that he had recently detected 

 Eozoon in a specimen of Ophicalcite from Cesha Lipa in Bohemia, in 

 a specimen of gneiss from near Moldau, and in a specimen of ser- 

 pentinous limestone sent to Sir Charles Lyell by Dr. Gumbel of 

 Bavaria. 



XXI. Intelligence and Miscellaneous Articles. 



ON THE MEASUREMENT OF SMALL FORCES BY MEANS OF THE 

 PENDULUM. BY MM. JAMIN AND BRIOT. 



V7S7HEN a spherical ball, suspended by a flexible wire attached to a 

 * " fixed point, is removed but a little from the vertical, and has im- 

 parted to it a very small initial velocity in any direction, its centre de- 

 scribes approximately an ellipse situated on a horizontal plane. When 

 the amplitude of the oscillations is sufficiently small, the two axes of 

 the ellipse may be regarded as constant in magnitude and in direction. 

 If there is no initial velocity, the small axis of the ellipse is equal to 

 zero, and the motion is in a plane. 



But if on the pendulum in motion a force is made to act other 

 than that of gravity, and relatively very small, this force produces 

 in the elliptical motion of the pendulum modifications or perturba- 

 tions which we propose to study. 



We first treated the question analytically by aid "of the method 

 of the variation of constants devised by Lagrange. The constants or 

 elements in this case are four ; that is, half the major axis a of the 

 ellipse, half the minor axis b, the angle a which the major axis 

 makes with a fixed right line, and the time r of the passage to the 

 summit of the major axis. Denoting by R what may be called the 

 perturbing function, the differential equations of the disturbed 



