PhUvsophical Transactions. S6Q 



glue can scarcely be made to adhere to the skin; whereas, the 

 free acid of the chemical ink partly dissolves the gelatine of the 

 MSS., and the whole substance adheres as a mordant." 



The earliest parchment manuscripts are probably the Codices 

 Rescripti, discovered in the libraries of Milan and of Rome ; 

 in these, time has destroyed the vegetable matter of the ink, 

 but solution of galls revives its blackness. 



I have tried several substances for restoring colour to fhe letters in an- 

 cient MSS. Tlie triple prussiale of potash, used in the manner recom- 

 mended by the late Sir Cmaules Blagden, with the alternation of acid, I 

 have lonnd successful , but by making a weak solution of it with a small 

 tiuantity of muriatic acid, and by applying them to the letters in their state 

 of mixture with a camel's hair pencil, the results are still better. 



After all, we have probably sustained no great loss in the 

 destruction of the Herculanean manuscripts ; no fragments of 

 Greek, and very few of Latin, poetry have been found in the 

 whole collection, and the sentences which have been made out 

 shew that the works are of the same kind as those before ex- 

 amined, and belong to the schools of the Greek Epicurean phi- 

 losophers and sophists. 



3. Observations on Naphthaline, a peculiar substance resembling 

 a concrete Essential Oil, which is apparently produced during 

 the decomposition of coal-tar, by exposure to a red heat. By 

 J. Yi\M,ll\..I>., Professor of Chemistry, Oxford. 



This is the very singular substance of which an account has 

 already been given in this Journal (Vol. VIII. p. 287), but upon 

 which no distinctive name had then been bestowed ; the most 

 important deficiency in its chemical history is unfortunately not 

 supplied by Dr. Kidd. " With respect to the elementary con- 

 stitution of this substance," he says, " I am not enabled to give 

 any satisfactory information." 



4 On the Aberrations of Compound Lenses and Object Glasses. 

 By J. F. W. Ilcrschel, Esq. F.R.S., &c. 



In this elaborate and truly important paper Mr, Ilcrschel 

 presents, under a general and unifurm analysis, the whole 

 theory of the aberrations of spherical surfaces, and furnishes 

 practical results of easy computation to the artist, disentangled 

 from all algebraical complexity, and applicable, by interpola- 

 tions of the simplest possible kind, to all the ordinary varieties 

 of the materials on which he has to work. 



