ject of considerable interest in geology, as tending to identify the 

 products of the ancient seas in their most minute particulars with 

 those of the present ocean. The results of his inquiries are given in 

 the form of a table, in which the springs, whose waters he examined, 

 are classified according to the geological position of the strata from 

 which they issue, and of which the several columns exhibit the total 

 amount of their saline ingredients; the nature and proportion of each 

 ingredient, as ascertained by former chemists, or by the author him- 

 self; and lastly, where they contained either iodine or bromine, the 

 proportions these substances bear to the quantities of water, and like- 

 wise to the chlorine also present in the same spring. He finds that 

 the proportion of iodine to chlorine varies in every possible degree ; 

 and that even springs which are most strongly impregnated with com- 

 mon salt are those in which he could not detect the smallest trace 

 of iodine. The same remark, he observes, applies also to bromine ; 

 whence he concludes, that although these two principles may, per- 

 haps, never be entirely absent where the muriates occur, yet their 

 relative distribution is exceedingly unequal. The author conceives 

 that these analyses will tend to throw some light on the connection 

 between the chemical constitution of mineral waters and their medi- 

 cinal waters. Almost the only two brine springs, properly so called, 

 which have acquired any reputation as medicinal agents, namely, 

 that of Kreutznach in the Palatinate, and that of Ashby-de-la-Zouch 

 in Leicestershire, contain a much larger proportion than usual of bro- 

 mine, a substance, the poisonous quality of which was ascertained 

 by its discoverer Balard. The author conceives that these two re- 

 cently discovered principles exist in mineral waters, in combination 

 with hydrogen, forming the hydriodic and hydrobromic acids, neu- 

 tralized 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 sub- 

 stance were to arise. 



Experiments to determine the Difference in the Number of Vibrations 

 made by an Invariable Pendulum in the Royal Observatories of 

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

 Artillery, Sec. R.S. Read March 25, 1830. [Phil. Trans. 1830, 

 ja. 239.] 



The invariable pendulum, No. 12, with which the experiments 

 recorded in this paper were made, was vibrated in the Royal Obser- 

 vatory at Greenwich in July 1828 ; in the Royal Observatory at Al- 

 tona 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, give 

 the rate of this pendulum at Greenwich to be compared with its rate 

 obtained at Altona. The details of all these series of observation* 

 are given in a tabulated form. 



2 D 2 



