941 



The paper contains an analysis of these salts. 



The mosses and lichens were also found to yield fucusol. The 

 ferns, on the other hand, yield a peculiar oil, which differs both from 

 fucusol and furfurol, possessing properties intermediate between 

 them. 



The results of these experiments seem to indicate some curious 

 botanical relations, as it appears highly probable that the matiere 

 incrustante is the same in all phanerogamous plants as they yield 

 furfurol. On the other hand, the matiere incrustante in the Algae, 

 mosses and lichens, as it yields fucusol and not furfurol, though the 

 same in each of these classes, is evidently different from that of pha- 

 nerogamous plants. The matiere incrustante of ferns appears how- 

 ever to be dissimilar from either of the others, as it yields an analo- 

 gous but peculiar oil. 



April 25, 1850. 

 The EARL OF ROSSE, President, in the Chair. 

 M. Quetelet was admitted into the Society. 

 The following papers were read : — 



1 . " On the Temperature of Steam and its corresponding Pressure." 

 By John Curr, Esq. Communicated by J, Scott Russell, Esq., F.R.S. 



The author states that it is intended in this paper to propose a 

 simple law to determine the pressure of steam corresponding to any 

 given temperature, irrespectively of experiment, taking as the sole 

 datum, that the vaporizing point of water under a given pressure is 

 100 degrees, that number being taken to correspond with the scale 

 of Celsius ; also to construct formulae in accordance therewith ; and 

 afterwards to compare their results with the actual experiments of the 

 Academy of Sciences of Paris. He further states that the rationale 

 of the subsequent formulae is expressed as follows. Let it be con- 

 ceived that a given quantity of water is vaporized under the condition 

 that the pressure thereon is increased in the same ratio that the vo- 

 lume is increased, or that at intervals of temperature 1, 2, .S, &c. the 

 volume is increased the same or in equal proportions ; the tempe- 

 rature of the volume will be increased exactly as the square of the 

 temperature indicated by the thermometer, supposing the instrument 

 to be a true measure of temperature, and as the square of the vo- 

 lume ; and the same of the pressure. 



Steam being generated from an indefinite quantity of water and 

 confined within a limited space, as in the usual boiler, he considers 

 the foregoing case is reversed; for the volume being constant, the 

 action of the fire is entirely exerted in producing increased elastic 

 tension of the vapour ; therefore the temperature of the steam at the 

 interval 1 to 2 degrees is increased inversely in the duplicate ratio 

 of the ratio in the case first described ; that is, the pressure is in- 

 creased directly at the square of the square, or fourth power of the 



