514 Horury Observations at Calcutta, [Skpt. 



10. — Sulphuret of Molybdenum. 

 This was put into my hands by a mercantile house in Calcutta, with- 

 out however noticing whence it came. 



It resembled graphite or plumbago so exactly in its qualities of 

 drawing traces on paper, of being unaltered in the fire, and very gra- 

 dually disappearing, that I should have been contented with these 

 appearances, had not its specific gravity, 4*64 to 45, been so much 

 higher than that of graphite, (1'4.) When heated also, white fumes, 

 devoid of smell, or slightly sulphurous, were perceived at the moment 

 of withdrawal from the fire. 



It was digested with disengagement of red fumes in nitric acid ; leav- 

 ing a white insoluble precipitate in the filter, weighing 74'4 per cent. 

 The liquid gave immediate evidence of sulphuric acid, that had been 

 formed from the sulphur present. The white mass acted in all respects 

 like molybdic acid, and was known to be so from its peculiar property 

 of turning instantly blue on contact with metallic iron, lead, copper, 

 or silver: a fact, I believe, not hitherto noticed : water is required 

 to produce this effect. Heated red with carbonate of soda, the metal 

 was reduced with effervescence. 



I am not aware that this singular mineral is turned to any profit, 

 but it is desirable to ascertain where it has been discovered. The 

 highspecific gravity of the Ceylon graphite, 2*37, leads me to imagine 

 that I may have mistaken that mineral also, and invites further inquiry. 

 It may be remembered*, that in an English cabinet of minerals, a me- 

 tallic ore was also found substituted for the true Borrowdale plumbago. 



IX. — Horary Meteorological Register for Calcutta. By J as. Prinsep, 



Sec. 8(C. 



The 21st September having been appointed one of the days for the 

 combined series of horary observations, by the Meteorological Associ- 

 ation, I could not allow it to pass without an attempt to fulfil the 

 prescribed terms, even at the sacrifice of a night's rest. 



The weather was not very favorable, although such as might be 

 expected near the equinox : the barometer was gradually falling, indi- 

 cative of blowing weather ; which in fact followed a few days after- 

 wards. The occasional violent showers checked the course of the 

 thermometer and hygrometer ; and the minimum temperature noted, 

 was that of the rain, rather than that of radiation to the sky. As a 

 different barometer was necessarily used during the night, care was 

 taken to continue its readings during the day, to obtain an accurate 

 comparison with the standard instrument at the Assay Office. The 

 difference — '017, has been added, to bring the whole to terms of the 

 * See Analysis of Graphite, Gleanings, vol. III. p. 180. 



