compressibility of Water to Practical Purposes. 39 



column, the instrument being attached to the sounding-lead. I 

 have been informed that the ingenious Mr Perkins proposed 

 this application of the compressibility of water which naturally 

 arose from his method of ascertaining the fact of compression 

 by using the pressure of the ocean, though no notice of this is 

 taken in his paper in the Philosophical Transactions. The 

 Piezometer there described was, like Oersted's instrument, in- 

 tended for measuring compressibility, not pressure. 



In these cases, a Register Thermometer would need to ac- 

 company the self-registering instrument. Probably no consi- 

 derable error is to be feared from abrupt changes of volume to 

 which the water might be subjected, for the coincidence of the 

 velocity of sound in water, theoretically deduced from its modu- 

 lus of elasticity, and experimentally by M. Colladon, seem to 

 prove that little or no heat is developed during its compression. 



The accompanying thermometer would, of course, require to 

 be itself protected from the disturbing influence of pressure. 



The extensibility of the glass vessel containing the water un- 

 der pressure, might be applied to give an independent confirma- 

 tion of the first result ; and elegant practical constructions might 

 be pointed out by which these separate results might be ob- 

 tained, and also the effect of temperature eliminated ; but with 

 these I forbear at present to trouble the Society. 



Upon the Egyptian Hieroglyphical Writing* By M. ARAGO.*f° 



The word Hieroglyphic, whether regarded metaphorically, or 

 in its natural acceptation, transports us to a region which has 



* The above is part of the Historical Eloge on Dr Thomas Young, which was 

 read to L' Academie des Sciences, in the month of November 1832. 



t It was thought by some, that at the time when the Chamber of Deputies was call- 

 ed to decide upon the national acquisition of the manuscripts of M. Champollion, and 

 upon the situation of his widow, it would be important for the members of that body to 

 have before them a simple and concise analysis of the great discovery of the phonetic 

 alphabet of the ancient Egyptians, and the interesting discussion which has arisen out 

 of it. M. Arago, who, in drawing up the Historical Eloge of the illustrious Dr Young 

 for the Academie des Sciences, was necessarily led to discuss this question, has kindly 

 yielded to the request of the friends of the late M. Champollion, and has supplied 

 them from this production, which has not yet been published, the whole of the part 

 which relates to hieroglyphics. In thus printing it for circulation among the members 

 of the two Chambers, the friends of Champollion cannot entertain a doubt that it will 



