I. On Crookes’s force

Author:

Abstract

In two papers by one of the authors of the present communication, which appeared in the Philosophical Magazine for March and April 1876, it has been shown that the motion of the blackened disks of a Crookes's radiometer can be explained by the known dynamical properties of the trace of gas which is present, and the term “ Crookes s force is pioposed to designate the reaction which comes into play between the blackened disks and the walls of the exhausted chamber when a difference of temperature exists between them. Shortly after the first of these papers appeared we commenced an experimental investigation of the subject with the view of learning, if possible, the laws to which the force conforms. The investigation is still in progress, and, being ex­ceedingly tedious, it will require a great expenditure of time before it is completed; we propose, however, in this preliminary paper to describe the apparatus and methods of observation employed, and to give some of the results already obtained. If the pressure which is exerted on the blackened pith surfaces reacts on the sides of the glass envelope, it follows that a transparent disk delicately suspended close to a stationary disk of blackened pith ought to move away from the pith, and therefore towards the light, when the pith is illuminated. This inference was submitted to the test of ex­periment by means of an apparatus represented in fig. 1 and constructed as follows :—A piece of elder-pith 2·5 centims. in length and 1·2 centim. in breadth, blackened on one side, was fastened by one end to the interior surface of the bulb of an ordinary boiling-flask (of about 200 cub. centims. capacity) in such a manner that the free end of the pith extended towards the middle of the bulb. A light glass rod with a small magnet on one end, and a disk of thin microscope-glass on the other end, was so suspended in the bulb that the glass disk could be readily balanced in a position nearly parallel with the surface of the blackened pith, and a few millims. distant from it. The silk fibre from which the glass rod was sus­pended hung from a fixed arm at the upper end of a tube, the lower end of which was hermetically fastened into the neck of the flask. An elongation of this tube (not shown in the figure) with a contraction for sealing, served to connect the apparatus with the exhaust-tube of a Sprengel pump. The pump was set in action, and occasionally the flame of an ordinary gas-burner was held at a distance of about 10 centims. from the blackened pith, while the microscope-glass was closely watched. When the gauge of the pump showed a tension of 7 millims., as com­pared with the mercurial column of a barometer standing in the same vessel of mercury, the glass disk was distinctly repelled from the pith and towards the source of light. As the exhaustion was continued the repulsion between the pith and the glass increased. The apparatus was sealed off from the pump when the mercury falling in the exhaust tube had for some days produced a metallic sound. Feeble illumination now caused the glass disk to be forcibly driven away from the pith.

Publisher

The Royal Society

Subject

General Earth and Planetary Sciences,General Environmental Science

Cited by 3 articles. 订阅此论文施引文献 订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献

同舟云学术

1.学者识别学者识别

2.学术分析学术分析

3.人才评估人才评估

"同舟云学术"是以全球学者为主线,采集、加工和组织学术论文而形成的新型学术文献查询和分析系统,可以对全球学者进行文献检索和人才价值评估。用户可以通过关注某些学科领域的顶尖人物而持续追踪该领域的学科进展和研究前沿。经过近期的数据扩容,当前同舟云学术共收录了国内外主流学术期刊6万余种,收集的期刊论文及会议论文总量共计约1.5亿篇,并以每天添加12000余篇中外论文的速度递增。我们也可以为用户提供个性化、定制化的学者数据。欢迎来电咨询!咨询电话:010-8811{复制后删除}0370

www.globalauthorid.com

TOP

Copyright © 2019-2024 北京同舟云网络信息技术有限公司
京公网安备11010802033243号  京ICP备18003416号-3