168 Intelligence and Miscellaneom Articles. 



As soon as the vitelline granules and germinal vesicle have dis- 

 appeared, the whole interior of the chorion is filled with a clear fluid, 

 in which a few granules and the germinal spot are seen to remain. 

 By swelling up this constitutes the embryonic vesicle and spot. A 

 membrane separates from the interior of the chorion, and contracting 

 on the granules forms a spherical yolk, in the centre of which is the 

 embryonic vesicle. This is the perfect ovum. The subsequent di- 

 visions of the embryonic spot, vesicle and yolk are described ; the 

 author particularly pointing out the gyrations of the embryonic ve- 

 sicle immediately after division. As soon as the whole interior of 

 the e^g has been filled by the subdivisions of the yolk, the external 

 granules coalesce and form a continuous membrane internal to the 

 chorioi], which by gradual depression on one of its sides forms first 

 a fleshy cup, and then, as the membrane of its concavity touches that 

 of its convex surface, acquires the form of a ring. The ring divides 

 at some point of its circumference, the extremities become pointed, 

 and thus the young Ascaris receives its characteristic shape. The 

 author has frequently repeated his observations with a view to their 

 verification, and has employed the camera lucida to render the illus- 

 trative figures as accurate as possible. 



XXVI. Intelligence and Miscellaneotis Articles. 



PENDULUM EXPERIMENTS. BY THOMAS G. BUNT. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, Bristol, July 24, 1851. 



IN my last letter I gave the particulars of eleven experiments, 

 each performed with a single impulse of the pendulum> and of from 

 one to four hours' duration, in which the effect of ellipticity was dis- 

 regarded, and the mean arc of vibration for the most part less than 

 eighteen inches. This series of experiments I have since consider- 

 ably extended ; their average duration has been increased to nearly 

 twelve hours, and the initial arc reduced to about twelve inches. I 

 have already stated, that 1 find a reduction of the arc of vibration to 

 be accomj)anied by a diminution of the elliptic error ; one-tenth of 

 an inch of ellipticity causing an apsidal motion of 0°'7 per hour on 

 a mean arc of about seven feet, and only 0°'06 per hour on an arc 

 of eleven inches. I have also found, that, in the case of my pendulum, 

 the direction which the elliptic motion assumes in the first quadrant 

 of the circle is changed, in the second quadrant, into its opposite ; 

 and that it is almost invariably the same in the same part of the 

 circle. 'I'hus, between 15° and 70° the elliptic motion is retrograde ; 

 between 70° and 90° it almost disappears; from 90° to 150° it is 

 direct; and from 150° to 0° (or 180°) it again becomes nearly imper- 

 ceptible. Hence it appears, that if the pendulum be set in motion 

 with a very small arc, and left to vibrate for a period of fourteen or 

 fifteen hours, the elliptic errors will not only be everywhere incon- 

 siderable, but will also tend in a great measure to neutralize each 



