M. Utzschneider on M. Guinand's Glass for Telescopes. 351 



18. Ostrea costata (Soz«.). Brad. clay. N. of Fr. (Bubl.). Great oolite. 



Anclift", near Bath (Cookson). 



19. — — pectinata. Oxford clay. N. of Fr. (Bobl.)- 



20. pennaria. Oxford clay. N. of Fr. (Bobl.). 



21. flabelloides(La;«.). O.zybrt/ c%. N. of Fr. (Bobl.). 



22. laeviuscula (Sow.). Lias. Eng. (Sow.). 



23. ■ obsciira {Sow.). Great oolite. Ancliff, near Bath (Cookson). 

 1. Gryphasa chamaiformis (P/i«7.). C«/r. gn'^. Yorks. And Oo/iVe Suther- 

 land (Phil.). 



9. bullata "(Sow.). Coral, oolite? Calc. grit? (PhW.). Oxford 



clay. Lincolnshire (Sow.). Oolite of Braambury Hill, 

 Brora (Murch.). 



3. inhserens (PAjY.). Ca/c.gn^. Yorks. (Phil.). 



4. dilatata {Sow.). Kelt. rock. Yorks. (Phil.). Oxford clay. 



Mid. and S. Eng. (Conyb.). Oxford elay and lias. Norm. 

 (DeC). Oxford clay. N. of Fr. (Bob!.). Oxford clay. 

 Burgundy (Beaum.). Great arenaceous formation. West- 

 ern Islands, Scotl. (Murch). 



5. — ^— incurva {Sow.). Lias. Yorks. (Phil.). Lia.i. Mid. and S. 



Eng. (Conyb.). Lias. Norm. (De C). Lias and inf. 

 oo/j/e. N. of Fr. (Bobl.). I,(as. S. of Fr. (Dufr.). Lias. 

 Metz, Salins, Amberg. (Brong.). Lias. Western Islands, 

 Scotl. Lias. Ross and Cromarty, Scotl. (Murch.). 



6. ? nana {Sow.). Lias and Oxford clay} N. of Fr. 



(Bobl.). 



[To be continued.] 



L. On M. Guinand's Glass for Telescopes. By M. 

 Utzschneider*. 



T ADDRESS you, Sir, as a friend to truth, in order to re- 

 -*■ move some unfavourable impressions which have got abroad 

 relative to my manufactory of glass for optical purposes. 



It is stated in the Bihliotheque Universelle (November 1828, 

 page 175) that the 9-inch object glass, belonging to the Dorpat 

 telescope, made by Utzschneider and Fraunhofer, came from 

 the crucibles of M. Guinand. 



Several other journals also have repeated, from the Globe 

 (French nevv^spaper) of November 1828, that MM. Thibeau- 

 deau and Bontemps had, in concert with M. Guinand the 

 son, re-discovered the secret of producing flint glass of any 

 magnitude, highly favourable for optical purposes ; a secret 

 which they pretend has been lost since the death of Fraunho- 

 fer, and Guinand the father : and that amongst the pieces 

 presented to the Academy of Sciences, there were some of 

 fijurteen inches diameter. 



* From Stiiumacher's Astron, NachriclUcn, No. 103. 



I do 



