piece of glass; and so easily distingish, without seeing either end, whether any Cylinder of glass I look’d on, were a solid stick, or a hollow cane.  And by this means, I could also presently judge of any small filament of glass, whether it were hollow or not, which would have been exceeding tedious to examine by looking on the end.  And many such like ways I was fain to make use of, in the examining of divers other particulars related in this Book, which would have been no easie task to have determined meerly by the more common way of looking on, or viewing the Object.  For, if we consider first, the very faint light wherewith the object is enlightened, whence many particles appear opacous, which when more enlightned, appear very transparent, so that I was fain to determine its transparency by one glass, and its texture by another.  Next, the unmanageableness of most Objects, by reason of their smalness, 3.  The difficulty of finding the desired point, and of placing it so, as to reflect the light conveniently for the Inquiry.  Lastly, ones being able to view it but with one eye at once, they will appear no small obstructions, nor are they easily remov’d without many contrivances.  But to proceed, I could not find that water, or some deeply ting’d liquors would in small ones rise so high as one would expect; and the highest I have found it yet rise in any of the pipes I have try’d, was to 21 inches above the level of the water in the vessel:  for though I found that in the small pipes it would nimbly enter at first, and run about 6 or 7 inches upwards; yet I found it then to move upwards so slow, that I have not yet had the patience to observe it above that height of 21 inches (and that was in a pretty large Pipe, in comparison of those I formerly mentioned; for I could observe the progress of a very deep ting’d liquor in it with my naked eye, without much trouble; whereas many of the other pipes were so very small, that unless in a convenient posture to the light, I could not perceive them:) But ’tis very probable, that a greater patience and assiduity may discover the liquors to rise, at least to remain suspended, at heights that I should be loath now even to ghess at, if at least there be any proportion kept between the height of the ascending liquor, and the bigness of the holes of the pipes.

AN ATTEMPT FOR THE EXPLICATION OF THIS EXPERIMENT.

My Conjecture, That the unequal height of the surfaces of the water, proceeded from the greater pressure made upon the water by the Air without the Pipes ABC, then by that within them[8]; I shall endeavour to confirm from the truth of the two following Propositions: