Page:Proceedings of the Royal Society of London Vol 1.djvu/455

Rh cumstances as the creeper, its tendrils manifested the same tendency to recede from the light. When ﬁrst emitted, they pointed upwards; but the angle gradually increased, and ultimately they pointed di- rectly downwards when no object was within their reach to which they could attach themselves. The ultimate direction was in all in- stances towards the darkness of the ground, whether the plants were trained upwards, horizontally, or downwards.

There was, however, this difference observable between the ten- drils of the vine and those of the Virginia creeper : those of the vine could be made to return to any position which they had quitted, by changing the direction of the light; but those of the creeper never returned to a situation from which they had once receded; as the tendrils of the vine are, moreover, separated into two divisions, they do not often fail of coming into contact with adjacent objects; and the eﬁ'ect of contact is almost immediately visible. They bend more ﬁrmly toward the body, and attach themselves by twining round it.

The organization of the tendril, by which it is adapted to perform these motions, appears to the author very similar to that of the young succulent shoot. It is abundantly provided with vessels; and it seems not improbable that a very considerable quantity of the moving ﬂuid of the plant passes through them, and that there is a close connexion between their vascular structure and their motion, as appears more especially in the act of grasping an object. The external pressure of the body on one side will probably impede the motion of the ﬂuids on that side of the tendril, and occasion greater extension of the oppo- site side in giving passage to a greater proportion of sap. In con- formity to this explanation, it is observed, that the sides of the ten- drils that are in contact with the substance embraced are visibly com- pressed and ﬂattened.

After tracing the history of the several measurements that have been made from time to time in different parts of the world, the author observes, that little doubt would have remained as to the earth being ﬂattened at the poles, had not the English measurement given an opposite result; the degree at the northern extremity being found equal to 60,766 fathoms, while that at the southern appeared to be 60,884.

Colonel Mudge’s estimate of the linear measure of a degree is made by dividing the number of fathoms measured in linear extent of an are by the number of degrees and parts of a degree ascertained by observations of stars. Don Joseph Rodriguez has followed a different course. He assumes as data the linear extent of Col. Mudge's base line, and the horizontal angles of his triangles ascertained by observation. He assumes, also, that the ﬁgure and dimensions of theearth