An essay of the great effects of even languid and unheeded motion whereunto is annexed An experimental discourse of some little observed causes of the insalubrity and salubrity of the air and its effects / by the Honourable Robert Boyle ...

To the VIIIth. Chapter.

Observation I.

IT may add probability to some things deliver'd in this Chapter and in divers other Passages of this Treatise, if I here recount a strange Phoenomenon, that came into my me∣mory whilst I was running over those Parts of this Discourse.

The Phoenomenon, in short, was this. Having met with divers pieces of transparent Glass, which I had rea∣son to think to be of a Texture or Temper very differing from ordina∣ry Glass, I thought fit to try, whe∣ther some of them were not far more springy and brittle than their thick∣ness would make one expect. And accordingly, though I found several wherein the Experiment would not succeed, especially if their figure were not convenient, yet with some others, I had very good success, and

particularly with some that were shap'd almost like the sharper End of the neck of a Retort. For though these pieces of Glass were much thic∣ker than such necks are wont to be, being perhaps 6 or 7 times as thick as common drinking Glasses, yet I more than once made the Tryal succeed so well, that, by obliquely scratching them, or tickling them if I may so speak, on the inside with the head or point of a Pin, they would forceably burst into many pieces in my hand. In which surprizing Phoenomenon, the matter of the Glass seem'd to contri∣bute something to this odd Effect, of so languid a motion, but much less than the Texture, or Tension, it ob∣tain'd by the peculiar way of order∣ing it in the Fire and the Air.