Aslroiiomlral Society. 217 



marl provincially termed "malen," which occurs in the same 

 alluvial tract. In one place several human skeletons have been 

 taken out of the marl. 



A paper entitled, Observations on the beds of clay, sand and 

 gravel, belonging to the red marl formation of the midland 

 counties, and on the rocks from which they are derived, by the 

 Rev. James Yates, M.G.S., was read in part. 



ASTRONOMICAL SOCIETY. 



March 11. — There was read "An account of the arrival and 

 erection of Fraunhofer's large Refracting Telescope at the Ob- 

 servatory of the Imperial University at Dorpat :" communi- 

 cated in' a letter from Prof Struve to Francis Daily, Esq. Pre- 

 sident. Prof. Struve received this telescope in November last, 

 and was happy to find that although it had travelled more 

 than 300 German miles, its several parts had been so carefully 

 packed that none of them had sustained the slightest injury. 

 When in a perpendicular position, the height of the object- 

 fflass is 16 feet 4 inches (Paris measure) from the floor, 13 feet 

 7 inches of which belong to the telescope itself;^ so that the 

 eye-glass stands 2 feet 7 inches from the floor. The diameter 

 of the object-glass is 9 Pari*, inches (about 9,f inches EngHsh). 

 The weight of the whole instrument is about 3000 Russian 

 pounds. It is so constructed that it may be used as an equa- 

 torial. The upper part of the instrument consists of the tube,^ 

 with its axis of motion, two graduated circles, and a variety of 

 levers and counterpoises, producing the most perfect equili- 

 brium in every direction, and providing against all friction. 

 The declination circle is divided from 10' to lO', but by means 

 of the vernier may be read off" to 5". The instrument may be 

 turned in declination with the finger, and round the polar axis 

 with still less force. 



The most perfect motion round the polar axis is produced 

 by means of clock-work, which is the principal feature of this 

 instrument, and the greatest triumph for the artist, the mecha- 

 nism being as simple as it is ingenious. A weight, attached 

 to a projection connected with the endless screw, overcomes 

 tlie friction of the machine. The clock vibrating in a circle 

 regulates the motion by moving an endless screw connected 

 with a second wheel in the above projection. The weight of 

 the clock as well as that of the friction may be wound up with- 

 out the motion being interrupted. When the telescope is thus 

 kept in motion, the star will remain ciuietly in the centre, even 

 when magnilii'd 700 times. At the same time there is not the 

 least shake or wavering of tlie tube, and it seems as if we were 

 observing an iuniioveable sky. 



Vol. «.■;. \o. 323. M^^;y7/ 1B25. Ee But 



