186 On the Chemical Compounds of [ Marcu, 
put down in the table to show the direction of the prevailing winds 5 
and the number of days which the winds have blown from each 
quarter in each month are selected with tolerable accuracy from our 
monthly journals. The 53 days denominated a clear sky, are those 
in which the sun has shone forth in all his splendour, without any 
apparent cloud; the 180 fine, cloudy, &c. are those in which 
different modifications of cloud have presented themselves to the 
observer, so as frequently to intercept the rays of the sun: and the 
133 rainy days are those in which rain has fallen, and that more 
than the =,th part of an inch in depth in the space of 24 hours : 
it should, however, be remarked, that many of this number have 
turned out fair and cloudy days. 
Artic.e III. 
On the Chemical Compounds of Axote and Oxygen: and on 
Ammonia. By John Dalton. 
(Read before the Literary and Philosophical Society of Manchester, 
Oct. 18, and Dec. 27, 1816.) 
Azore and oxygen are two of the most important chemical 
elements with which we are acquainted. In their most simple state 
they are exhibited to us in the form of elastic fluids, and possess 
various highly interesting properties, which may be seen in the 
elementary books of chemistry, and which it is not my present 
business to enumerate. ‘These two elastic fluids may be mixed 
together in any proportion, and soon become mutually diffused 
through each other without manifesting any mark of chemical 
union, except the simple circumstance of uniform diffusion. Mixed 
in the proportion of 100 measures of azote to 26} of oxygen, they 
constitute the principal part of that great and voluminous mass of 
elastic fluids—the earth’s atmosphere. Lavoisier first demonstrated 
the constituents of the atmosphere about 30 years ago. He does 
not seem to have had a clear idea of the kind of union between the 
two elements; for he uses the terms combination and mixture in- 
differently when speaking of the constitution of the atmosphere : 
thus, he mentions ‘‘ the mutual adhesion of the two constituent 
parts of the atmosphere ;” and “ there still remains a portion of 
respirable air united to the azote which the mercury cannot sepa- 
rate,” &c. (Elements of Chemistry, English translation, fourth 
edit. p. 86.) This language plainly indicates chemical vnion. 
In another place he says, “ the azotic gas may be procured from 
atmospheric air by absorbing the oxygen gas which is mixed with 
it, by means of a solution of sulphuret of potash,” &c. (P. 266.) 
In the table of binary combinations of azote with simple substances 
