326 '.Oh/ervatlons en a Miji at MaeJlrhU. 



II. 



X)hfervatms on a Mijl which prevailed at Maeflricht on the \\ih Nivofe, in the Tear 8, h'j 

 CiT. Paisse, -with Remarks by CiT. Parmentier*. 



JLT is of great importance in the accurate fclences to pay attention to all the circumftances 

 upon which obfervations can be founded. If this part of natural phifofophy were culti- 

 vated with tlie care it deferves, there is no doubt but we fliould be much more intimately 

 acquainted with the influence of meteors on the health of men, which it fo evidently 

 affeiSls. Thofe fogs which are almoft periodically renewed, prefent to the minifters of 

 health an extenfive field of obfervation, from which it fliould appear, that the moft ufeful 

 confequences refpedling the origin of difeafes may be deduced. 



The mid which forms the fubje£t of the prefent communication was fo peculiar in its 

 appearance and etFe£ts, that I have concluded that it might be of advantage to give a de- 

 tailed account of the fame. 



On the morning of the nth Nivofe Reaumur's thermometer had defcended to 13^° 

 below O, where it remained for moft part of the day, with no greater variation than i a. 

 degree. At feven in the evening it was conftant at the fame temperature, and the follow- 

 ing day at feven in the morning it had rifen two degrees above the freezing point, and at 

 eleven o'clock the thaw had unequivocally taken place at the temperature of 5 degrees. 

 At two in the evening the thermometer marked 6^ degrees, the thaw continuing ; about 

 five in the evening a flight mift appeared, which continued till half paft feven ; at eight it 

 was intirely diflipated, and the moon (hone bright, at which time the thermometer de- 

 fcended again within four degrees of the freezing point ; at nine its elevation did not exceed 

 one degree, when the fnow began to harden. On the 13th at feven in the morning the 

 thermometer flood at feven degrees above O ; at nine, eight degrees, and at noon it rofe to 

 the ninth degree, and the fun which appeared from time to time in the courfc of the day 

 had confiderable force. The thermometer kept at the fame elevation, and the thaw con- 

 tinued its progrefs at eight in the evening. 



On the 14th day of the month the horizon was covered with a mIft of inconfiderable 

 denfity. It appeared like an evaporation from the earth arifing about a metre above the 

 furface. At nine it rofe to the height of feveral metres without becoming lefs denfe ; at 

 eleven it became more confiderable ; and at noon it was fo thick that two perfons at a very 

 fmall diftance afunder could not fee each other without much difiiculty. At three in the 

 evening its denfity was ftill greater, and its fmell fo fetid as ftrongly to impede refpiration. 

 The thermometer during this time underwent no greater change than half a degree, not 

 paffing beyond the ninth degree. The fmell and acrid effe£ls of this meteor were fo dif- 



t Annales de Chimie, XXXIII. 217< 



agreeable. 



