194- 



tions of Mr. Biggin and Mr. Davy, which show that the proportion 

 of tan in the same trees is different at different seasons, and that it 

 is principally contained in the white interior bark, which bark is 

 comparatively most abundant in young trees, he observes, that there 

 seems to be an intimate connexion between the formation of new 

 wood and the formation of tan, in those vegetables which afford the 

 latter; and thinks it very probable that such vegetables have the 

 faculty of absorbing more carbon and oxygen than is required in 

 the formation of the vegetable principles, especially of the woody 

 fibre ; arid that this excess of carbon and oxygen, by chemical com- 

 bination, becomes tan, which is secreted in the white interior bark, 

 and afterwards decomposed, and employed in the formation of the 

 new wood. 



The ligneous substance of vegetables, Mr. Hatchett says, appears 

 to be composed of carbon, oxygen, hydrogen, and nitrogen ; and he 

 has reason to think, from some synthetical experiments he has made, 

 that tan consists of 53 parts of pure carbon, and 47 of oxygen. 



In the concluding section, Mr. Hatchett observes, that the whole 

 of the present paper may be concentrated into one simple fact, 

 namely, that tan is composed (at least essentially) of carbon and 

 oxygen ; and that, although it has hitherto been deemed a peculiar 

 principle, formed by nature in certain vegetables, it may, with the 

 greatest ease, be produced, by presenting oxygen to carbon in the 

 humid way, under the circumstances which have been described. 



Since the experiments which have been related were made, Mr. 

 Hatchett has, he says, further proved the efficacy of the factitious 

 tan by actual practice ; as he has converted skins into leather by 

 means of tan produced from materials which, to professional men, 

 must appear extraordinary, such as deal sawdust, asphaltum, turpen- 

 tine, pit-coal, wax candle, and a piece of the same sort of skin. 

 Allowing, therefore, that the artificial production of tan must for the 

 present be principally regarded only as a curious chemical fact, not 

 altogether unimportant, yet, as the principle on which it is founded 

 has been developed, we may, Mr. Hatchett thinks, hope that a more 

 economical process will be discovered, so that every tanner may be 

 enabled to prepare his tan, even from the refuse of his present ma- 

 terials. 



The Case of a full-grown Woman in whom the Ovaria were deficient. 

 By Mr. Charles Pears, F.L.S. Communicated by the Right Hon. 

 Sir Joseph Banks, K.B. P.R.S. Read May 9, 1805. [Phil. 

 Trans. 1805,;?. 225.] 



The woman whose case is here described was born in Radnorshire 

 in the year 1770. She was of a fair complexion, and, except when 

 irritated, of a mild temper. In her diet she was remarkably abste- 

 mious, eating very little, either of animal or vegetable food ; and if 

 at any time she ate a hearty meal, or took several kinds of food, she 

 was so much affected by it as to faint. She was of a costive habit, 



