This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1866 edition. Excerpt: ... the escapement? The answer to this question is very similar to those already given, when speaking of the proportions of the pallet. Any increase of length on the lever will require a greater radius of impulse, or a greater distance of the impulse-pin from the balance-centre, if the angle of lifting shall remain the same, and consequently the arc of intersection will be longer, and the friction of the acting parts must augment in the same ratio. The force transmitted both in the unlocking-and the impulseaction is the same, whether the lever be long or short, provided the angles performed and the proportions of lever-length and impulse-radius remain the same in both cases, and the only difference consists in the greater breadth of intersection, and the increased friction connected with the long lever. These considerations would lead to employing as short levers as possible, but it must be observed here, that the forementioned diminution of the intended effect of movement, by the necessary side-shake in the pivot-holes, must be taken notice of, because the loss, arising from this circumstance, though an absolute quantity, is in very different proportions to the extent of the distance to be performed by the fork and roller-action. Therefore it is advisable not to go too far in either direction, and it may be esteemed a good proportion to make the lever not so long as to allow its arbor standing beyond the circumference of the balance. One consequence of the short lever in all 3/ platewatches will be, that ithe pallet-arbor must be made veiy short and the escape-pinion too, if the escapement is not set in straight line, but the advantages of diminished friction outweigh this little defect of construction so much, that we see all the...

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A General History of Horology describes instruments used for the finding and measurement of time from Antiquity to the 21st century. In geographical scope it ranges from East Asia to the Americas. The instruments described are set in their technical and social contexts, and there is also discussion of the literature, the historiography and the collecting of the subject. The book features the use of case studies to represent larger topics that cannot be completely covered in a single book. The international body of authors have endeavoured to offer a fully world-wide survey accessible to students, historians, collectors, and the general reader, based on a firm understanding of the technical basis of the subject. At the same time as the work offers a synthesis of current knowledge of the subject, it also incorporates the results of some fundamamental, new and original research.