Proceedings of the Fifth Meeting of the British Association for the Advancement of Science Volume 5; Held in Dublin, During the Week from the 10th to the 15th of August, Inclusive - With an Alphabetical List of the Members Enrolled in Dublin (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1835 Excerpt: ...to boil in the shaving pot; the upper part of the scale of the thermometer being kept above the lid, so as to be readily seen. The heights are then obtained from the boiling points, by tables which are of easy access. He exhibited to the Section a com parison of the heights of certain elevated stations taken by the aid of his simple apparatus, With the heights of the same stations taken by methods of admitted accuracy, and in general the difference was only a very few feet, and never so great as to be of any practical importance. Mr. M'cullagh gave a short account of some recent investigations concerning the laws of reflection and refraction at the surfaces of crystals. To understand the nature of the general problem which a complete theory of Double Refraction requires to be solved, let it be supposed that a ray of light is reflected and refracted at the separating surface of an ordinary medium and a doubly refracting crystal; the light passing out of the former medium into the latter. This limited view of the subject is. taken merely for the sake of clearness of conception; since we might suppose that both media are crystallized, without increasing the difficulty of the problem. The question, it is obvious, naturally divides itself into two distinct heads. The first relates to the laws of the propagation of light in the interior of either of the two media, before or after it has passed their separating surface; and this part of the subject has been fully treated, according to their different methods, by MM. Fresnel and Cauchy. The second division of the subject had been left completely untouched. It relates to the more complex consideration of what takes place at the separating surface of the media; the laws according to which the light is there divided b...