1-818.] Philosophical Transactions for 1817, Part II. 53 



Upon the Extent of the Expansion and Contraction of Timber 

 in different Directions relative to the Position of the Medulla of 

 the Tree. By Thomas Andrew Knight, Esq. F.R.S. In a 

 Letter addressed to the Right Hon. Sir Joseph Banks, Bart. 

 G.C.B. P.R.S. 



Observations on the Temperature of the Ocean and Atmos- 

 phere, and on the Density of Sea Water, made during a Voyage 

 to Ceylon. In a Letter to Sir Humphry Davy, LL. D. F.R.S. 

 By John Davy, M.D. F.R.S. 



Observations on the Genus Ocythoe of Rafinesque, with a 

 Description of a new Species. By William Elford Leach, M.D. 

 F.R.S. 



The distinguishing Characters between the Ova of the Sepia 

 and those of the Vermes Testacea that live in Water, explained. 

 By Sir Everard Home, Bart. V.P.R.S. 



Astronomical Observations and Experiments tending to inves- 

 tigate the local Arrangement of the Celestial Bodies in Space, 

 and to determine the Extent and Condition of the Milky Way, 

 By Sir William Herschel, Knt. Guelp. LL.D. F.R.S. 



Some Account of the Nests of the Java Swallow, and of the 

 Glands that, secrete the Mucus of which they are composed. By 

 Sir Everard Home. Bart. V.P.R.S. 



Observations on the Hirudo Complanata and Hirudo Stagnalis, 

 now formed into a distinct Genus under the Name Glossopora 

 By Dr. Johnson, of Bristol. Communicated by Sir Everard 

 Home, Bart. V.P.R.S. 



Observations on the Gastric Glands of the Human Stomach, 

 and the Contraction which takes place in that Viscus. By Sir 

 Everard Home, Bart. V.P.R.S. 



On the Parallax of the Fixed Stars. By John Pond, Esq. 

 Astronomer Royal. 



In the history of the meetings of the Royal Society a general 

 account has been given of these papers,* but many of them are 

 of so much importance as to require a more detailed analysis. 

 Among these we may include Mr. Wollaston's description of his 

 thermometrical barometer. 



It has been long known that the temperature at which water 

 boils is diminished in proportion to the diminution of the weight 

 of the atmosphere ; and this principle had been pointed out by 

 Fahrenheit, and more lately by Cavallo, as a means that might 

 be employed for measuring altitudes. Mr. Wollaston has con- 

 trived an apparatus by which this may be accomplished, even 

 with more accuracy and convenience than the common baro- 

 meter. The two great objects were, first, that very small por- 

 tions of heat might be rendered perceptible; and, secondly, that 

 the instrument should be portable Both these objects are 

 attained by having the thermometer with a large bulb and a very 



* Annuls, ix. 323, 393, 468 ; x. 64, 13<>. 



