338 Analysis of Books. 



author conceives that these two recently-discovered principles exist 

 in mineral waters, in combination with hydrogen, forming the 

 hydriodic and hydrobromic acids, neutralized, in all probability, by 

 magnesia, and constituting salts which are decomposable at a low 

 temperature. He has no doubt that a sufficient supply of bromine 

 might be procured from our English brine springs, should it ever 

 happen that a demand for this new substance were to arise. 



2. Experiments to determine the difference in the Number of Vibra- 

 tions made by an invariable Pendulum in the Royal Observatories 

 of Greenwich and Altona. By Captain Edward Sabine, of the 

 Royal Artillery, Secretary to the Royal Society. [Read March 

 25, 1830.] 



THE invariable pendulum, No. 1*2, with which experiments recorded 

 in this paper were made, was vibrated in the Royal Observatory of 

 Greenwich in July, 1828; in the Royal Observatory at Allona in 

 September and October of the same year ; and again at the Royal 

 Observatory at Greenwich in August, 1829. The mean of the 

 results obtained at Greenwich in July, 1828, and in August, 1829, 

 gives the rate of this pendulum at Greenwich, to be compared with 

 its rate obtained at Altona. The details of all these series of obser- 

 vations are given in a tabulated form. 



3. Experiments to ascertain the correction for Variations of Tempera' 

 ture within the limits of the natural Temperature of this Climate, 

 of the invariable Pendulum recently employed by British Observers. 

 By the same Author. [Read March 25, 1830.] 



THE correction for temperature which the author deduces as the 

 general result of his investigation, is 0.44 of a vibration per diem 

 for each degree of Fahrenheit between 30 and 60. He considers 

 this result as entitled to the greater confidence, from the favourable 

 nature of the circumstances under which the inquiry was conducted ; 

 since the influence of natural temperature is more permanent and 

 equable than that of temperatures artificially produced. He consi- 

 ders it as desirable, however, that means should be devised of 

 extending experiments on this subject to a wider range of tempera- 

 tures. 



4. On a new Register Pyrometer, for measuring the Expansions of 

 Solids, and determining the higher degrees of Temperature upon 

 the common thermometric scale. By J. Frederic Daniell, Esq. 

 F. R. S. [Read June 17, 1830.] 



IN the year 1821, the author published in the Journal of the Royal 

 Institution, an account of a new pyrometer, and of some determi- 

 nations of high temperatures, in connection with the scale of the 

 mercurial thermometer, obtained by its means. The use of the 

 instrument then described was, however, limited ; and the author 

 was subsequently led to the invention of a pyrometer of a more 



