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or plates^ which^ vphen fingk^ fioevpd the OhjeU hnt laid 
upon one another^ Jhew d it double ; the two images appearing the 
more dijtant from one another, the greater the number was ofthofi 
thin plates laid on one another. With fubmiffion to better judge^ 
mentSy IthinliittobeaJ^indofSehmtes. Some of our curi- 
ous men here were of opinion^ that the Rhomboid j^^^re, proper 
to this Stone y was the caufe of the appearances doubled thereby. 
But having trytd^ whether in other Iran [parent Bodies^ of the 
like Figure^ the like would happen, we found no Juch thing in 
them 5 which made us fufpecf Jome peculiarity in the very Body of 
this Stone^ 
Thefe Letters being thus premlfcd, we now come to re- 
late the Brief of the Obftrvations and Experiments themfelvesi 
referring the more Curious Reader tt> the larger Actomptof 
them, and their Mathematical Demonftrations, as they are 
to be found in the Printed Book, entituFd Erafmi Barthelini 
Experiment a Cfjryfialii Ijlandici Dif-Diaclafiici 5 quibm mira 
In/olita KEFK ACT 10 detegitur. Hafni^ A. 8 669. 
I. The Inhabitants of //7^«^/ and our oM>n Merchants inform 
usj that this kind of Chryftal is found in divers places of that 
Country 5 but chiefly digg'd out of a very high mountainjUot 
far from the Bay of Roerfiord, which lies in 65, degr* Latitude-^ 
that Mountain reacheth Southvv^ard, and hath its whole 
outlide made up of this fubftance, without a neceflity of dig- 
ging deep for \i § that it is cut out by Iron-too!es, in big* 
nefiof a Cubicktoot, or fomewhat better: and that out of 
its corners there is fometimes found grown out a harder mat« 
rer, not unfit to cut giafs, of a figure different from that of 
the whole mafsjand approaching to that of Diamonds. 
2» The Figure of this Chryftal ftone is like a Rhombich^ot 
Rhomboid Prifme, ^ Nor hath the whole Body (hat Figure on- 
ly, but all the parts of it, when broken into fmall pieces,keep 
the fame 5 except that in fome cafes the ground, v^^hence 'tis 
digged 5 yields fuch as are of a . Triangular Pyramid- 
figure. 
5. This Subftance is Eleftricalj attrafting (to fpeak with 
the Vulgar)) when heated, ftraw, FeatherSj &c, 
LI a 3» le 
