7 4^8) 
Jufffcions {fox you know,ttet I do not call them fo much as opinions,') 
but for a weightier inducement, to be told you at the end of this 
Paper. 
The two chief things aimed at in the imperfeci Attempts I now 
fend you, were todifcover ; firjl^ whether, as fome Corrofionsof 
Bodies do in clofe VeflTels increafe the Spring of the Air ( as I long 
fince noted them to do5)fo fome other Corrofions may nor , by a 
contrary or fome other way, vpeaken the Spring of the Air ; and 
^ext^ whether in fome Solutions and Precipitations the Air on the 
account of fome unobferved Quality may not be found to produce 
fome PhxmmenA not yet taken notice of. 
In order to each of thefe Enquiries,! fliall mention a few Tryals, 
though without curiouflyforting them, becaufe fometimes in the 
lame Experiment both thofe Attempts were jointly profecuted* 
You may remember that in fome of my formerly publiftied Try- 
als I acquainted you with an odd Phenomenon of the Change of Co- 
lor producible in folutions of Copper by the operation of the Air j 
I fliall now add what further ThanomenA my Memory or Notes fup- 
ply me witb,aboUt the Subjefi of that and the like Experiments* 
Experiment the Firjl. 
We tookfiHngs of crude Copper, and put rbem intoaGryfta!- 
lin Glafs of a Conical fhape, into w hich we poiired fome ftrorg 
Spirit of Salt, (that was fitted for our peculiar purpofe) to the 
heighth of about a fingers breadth above the Filings ; and then clo- 
fing the Veflel witha Glars-ftopple exquifirly fitted to it, we fuf- 
fer'd it to continue unmoved in a Window for f:?me dayes, till the 
liquor had bothobtained a high and darkifli brown colour by the 
folutionof fome of the Copper, and loft that colour again, grow- 
ing clearlike common water, (which is it fel/a fomewbat odd Phe- 
nomenon;) and then taking out the ftopple, (without fliaking the 
liquor) and thereby giving accefsto the outward Air, wepercei- 
ved,(as we had conjeflur'd) that the upper furfaceof the liquor 
did in a few minutes re-acquire a darkifh brown colour, which pe- 
netrating deeper and deeper, at the end of about a quarter of an 
hour the wholebody of theliquorappear'd tobe litewife tinged. 
The Conical Glafs being again well Ropt^tMe Menflrmm did again 
in very few dales let fall or otherwife lofe its tincture ; which, the 
flopple beifng taken out, it re-gained as before. Nor were thefe 
two the only Tryals I made with the like fuccefs for the main ; but 
