Re: Reply 6 above - about the 1854 book "The World of Science, Art, and Industry ..."
At the end of page 152 is a reference to "
... the letter weights with interior clusters of flowers ...". This is in context of opening remarks leading to the descriptions on page 153 for methods (based on processes from "centuries past") of making drinking vessels, letter weights etc.
I have tried to set out in the quote below, a reduced version of parts of the page 153 text, with my own editing in square brackets:
.. ornaments of infinite variety [such as the "clusters of flowers" referred to on page 152] may be formed whose presence in letter weights has puzzled so many … fashioned at the blow-pipe table, out of the very spiral and colored rods whose origin has been already described; ... [Then] A mass of soft glass sufficient for the lower half of such a letter weight is now prepared, and upon its hot surface the colored floret or ornament is applied, while immediately another workman approaches with a second hemispherical mass of colorless glass which he applies upon the upper surface of the ornament. Thus one compound mass is produced having the ornamental glass in its centre, and after being duly fashioned, and annealed, and cut, forms the wonder which we see.
So, what is that referring to? It could be a domed paperweight having millefiori elements and possibly finished with facets. Or it could be a (larger) rectangular or circular letter weight including a mosaic pattern and finished with cut edges. And the text for "
glass sufficient for the lower half" and "
a second hemispherical mass ... applied to the upper surface" does not make it easy to understand what is being made.
The text is about products made in Murano around the 1850s. In those years, Murano domed paperweights were of the style of "scrambled, millefiori and filigri" set close to the surface of the dome. But that does not sound like a "compound mass ... having the ornamental glass in its centre".
So maybe it really is referring to a rectangular (or other shape) block with an internal (or centrally placed on the top) element of mosaic or millefiori.