jeftures offered upon the occafion. The prevailing 
opinion, however, attributed the formation of this 
paper to a cafual aggregate of the fibres of different 
kinds of filamentous plants, colled;ed together by the 
waters, and left on the furface of the ground at their 
retreat. This fuppofition Teemed plaufible enough, 
fince fuch a mechanifm could be produced only by 
filamentous plants j moft of which are commonly the 
fpontaneous produdlions of fuch low, marlhy ground. 
But upon confidering that, in the paper manufadures 
of different countries, various degrees and methods 
of maceration are requifite, according to the refpedlive 
qualities of the fibres of different plants ; it appeared 
to me very difficult to conceive, that a paper of fo 
delicate and uniform a texture as that of Cortona 
fiiould owe its origin to fo complicated and remote a 
caufe. 
To bring the matter in queftion to a more certain 
iffue, I therefore thought it neceffary to examine the 
threads of this paper with a good microfcope; and, 
agreeable to the opinion 1 had entertained, found 
them to confifi: of mere filaments of the common 
fpecies of Conferva, without the intervention of any 
other plant whatfoever. dt was eafy enough to afcer- 
tain the identity of the Conferva, the filaments of 
which it is compofed being of a peculiar ftrudture, 
and very different from thole of any terrellrial plant ; 
befides, as they are folitary in their natural ftate, they 
undergo no other alteration by the above mechanifm, 
than the lofs of the parenchyma that in veils them, the 
ftrudure of the filaments themfelves remaining as 
perfedl as ever. 
H 2 
To 
