vifible effe&s upon the rays of Light, without any other 
coefficient caufe : and then, that there is in the Air or Atmtr - 
jphere fuch a variety in the conftituent parts of it , both as 
to their denflty and rarity , and as to their divers mutations 
and portions one to another. 
He concludeth with two Celeflial Obfervations 5 where- 
of the one imports, what multitudes of Stars are difcove- 
rable by the Teleflope, and the variety of their magni- 
tudes : intimating with all , that the longer the Glafles are, 
and the bigger apertures they will indure, the more fit they 
are for thefe difcoveries : the other affords a defcription of a 
Vale in the Moon , compared with that of Hevelius and Ric- 
ciolo 5 where the Reader will find feveral curious and plea- 
(ant Annotations , about the Pits of the Moon , and the 
Hills and Coverings of the fame 5 as alio about the varia- 
tions in the Moon y and its gravitating principle 5 together 
with the ufe, that may be made of this Inftance of a gravity 
in the Moon . 
As to the Inventions of Art, deforibed in this Book, the 
curious Reader will there find thefe following 
1. A Barofcope , or an Inftrument to fhewall the Minute 
Variations in the FreJJnre of the Air ^ by which he affirms,, 
that he finds, that before and during the time of rainy wea- 
ther, the Preffure of the Air is lefs$ and in dry weather, 
but efpecially when an Eaflerly Wind which having part 
overvaff Tra&s of Land is heavy with earthy particles ) 
blows, it is much more, though thefe changes be varied ac- 
cording to very odd Laws,. 
2. A Hygrofcope, or an Inftrument , whereby the Watery 
fleams , volatile in the Air , are difcerned , which the Note 
it felf is not able to find. Which is by him fully defcribed 
in the Obferyation touching the Beard of a wild Oate , by the 
means whereof this Inftrument is contrived. 
3. An Inftrument for graduating Thermometers , to make 
them Standards of Heat and Cold. 
4. A New Engin for Grinding Optic kGlajfes , by means of 
which he hopes 5 that any Spherical GLafles, of what length 
foeve.%. 
