eral of the former Tracts; to which, as we have added, in this, the
_Quaeries_ about _Mines_, so we shall subjoyn those, that were not long
since committed to the care of that Excellent Promoter of Astronomy and
Philosophy, Monsieur _Heuelius_, Consul of _Dantzick_; who demonstrates so
much zeal for the advancement of real knowledge, that he not only improves
and promotes it by his own Studies, but labours also to incite others to do
the like; having already warmed many of the Northern Climate, particularly
_Poland_, _Prusse_, _Livonia_, _Sweden_ and _Denmark_, into a disposition
to be studious and active in inquiring after such particulars concerning
Philosophy, as are recommended from hence, and rendred them, very willing
to employ themselves in things of that nature.

_The Inquiries sent to _Dantzick_, are these;_

1. What Signior _Burattini_ (an _Italian_ Gentleman, Master of the Mint to
the King of _Poland_, and reputed a great Master in the _Mechanicks_) hath
perform'd in _Diopticks_? Whether at present he employs himself, as is
related, in grinding a _Telescope_ of 120 foot long? And, if so, what way
he means to make use {345} of, commodiously to handle a Tube of that
length?

2. Whether the same have the Art (as has been written from _Paris_) to make
such Glass, as is not at all inferiour to _Venice_-glass, and exceeds any
plate of Glass, hitherto made there, twice or thrice in bigness?

3. What is the way of making Pot-ashes in _Poland_?

4. What is to be observed about _Succinum_ or Amber? whether it be an
Exsudation of the Sea? whether it be seen to float upon the surface of the
Sea? whether it be soft, when 'tis first cast on shore? At what season of
the year, and in what manner 'tis taken up, &c?

5. What is to be observ'd in the Digging of _Sal Gemmae_ in _Poland_? what
is the Depth of the Mines, stored with this Salt? what their distance from
the Sea, &c?

6. What truth there is in that Relation concerning Swallows being found in
Winter under waters congealed, and reviving, if they be fish'd and held to
the fire?

7. Whether there be in the _Bodnick Bay_ a Whirl-pool, as is related to be
in the Sea of _Norway_, which is commonly call'd the _Maal-stroom_? And
whether there be any Signs, that speak the communication of those Gulphs by
subterraneous passages; as the Jesuit _Kircher_ affirms in his _Mundus
Subterraneus_ T. 1. p. 146?

8. To what depth the Cold in those parts peirces the Earth and Wat