SOS Proceedings oj Philosophical Societies, [April^ 



plus anciennes mines, a fixe les loix de succession des couches % 

 il a montie leur ancieDiiete respective et pursuivi chacune d'elles 

 dans toutes ses metamorphoses. C^est de lui, et de lui seule- 

 ment, que datera la geologie positive, en ce qui copcerne la 

 nature minerale des couches ; mais ni Fun ni I'autre n'a donne 

 a la determination des especes organisees fossiles, dans chaque 

 genre de couche, la rigueur devenue necessaire, depuis que les 

 animaux connus s'elevent a un nombre si prodigieux.'^ Tome i. 



Article X. 



Proceedings of Philosophical Societies, 



ROYAL SOCIETY. 



On Thursday the 25th of February the follov^^ing papers were 

 read 



An account of a new micrometer, by Dr. W. Hyde Wollas- 

 ton. It consists of an instrument similar in appearance to a 

 common telescope, with three sliding tubes. At one end there 

 is a spherical lens, with a focus of about -j-Vth of an inch ; and 

 within -^th. of an inch of it, there is a slit, through which 

 objects can be seen. Instead of the object glass there are a 

 number of parallel wires placed beside each other, of a deter- 

 minate diameter, as an object of comparison. Within are two 

 glasses, between which the object to be measiTred is put. Its 

 size is determined by comparing the magnified image with the 

 standing wires at the extremity, of the tube, and ascertaining 

 their distance from the eye when both appear of a size: 16* 

 inches distance in the instrument corresponds to a wire of y-q-u-qI) 

 of an inch in diameter, and S inches to one of —-y—th of an 

 inch. 



A paper on the winter solstice, by Mr. Pond, Astronomer 

 Royal. He found the obliquity of the ecliptic at the summer 

 solstice to be 23° 27' 51*5^^, and at the winter solstice 

 23^ 27' 47*37''. The difference he conceives to depend upon 

 refraction. He is endeavouring at present to ascertain whether 

 Dr. Bradley's allowance for refraction be correct. 



A paper on the black matter in the glands of the lungs in old 

 persons, by Dr. Pearson. The lungs are at first light coloured;; 

 but they become mottled about the age of 20, gradually increase 

 in darkness, and in old persons are nearly black. Dr. Pearson 

 examined the cause of this change, and found it owing to a 

 quantity of charcoal contained in the glands. This charcoal, he 

 conceives, is taken in with the breath, suspended in the air. He 

 accoufits for its absence in young persons^ and in brute animals 

 o 



