Another ramble from me ...
I think there is a bit of confusion here, but it's all very interesting, nonetheless. I checked with other PCC members about "hollow canes" used in Baccarat paperweights (this was easier and quicker than just scouring my books etc.) and I received some good pointers.
In Larry Selman's The Art of The Paperweight (1988)
, on page 76, in a section discussing millefiori canes, he includes a reference:
Hollow or tubular: The centers of these canes were made of clear glass, giving them a hollow appearance. Often the clear glass was surrounded by a cogwheel.
An example of the type of cane is seen perhaps more often in modern weights from St Louis rather than Baccarat. Here's one from the PCC 1999 Exhibition: http://www.kevh.clara.net/exhib99/Modern/French/StLouis/ModStLouisBouleRouge19.htm
The white cog canes, flashed in orange (or is it salmon-pink?) clearly have the look of being hollow but in fact have solid clear glass at the centre.
As Frank suggested, many makers from many countries have used canes with a clear glass centre. But perhaps the modern French designs, such as the St Louis one shown, have been the only ones to utilise these canes as a primary part of design - at least, visually?
Ray's reference to the text in the "Wheatonvillage" site is useful in that it gives a description of a process of collapsing clear glass around millefiori canes. But this is not the same as making "hollow canes".
In fact, the wheatonvillage text is a selective summary from two brief sections of the Apsley Pellatt book. In the "Venetian Ball" section, the item was described as being
... a collection of waste pieces ... packed into a pocket of transparant Glass ... adhesively collapsed ...
This process resulted in a solid mass which (probably) looked like an unevenly shaped bead but perhaps somewhat larger than regular beads of the time. The other section of Pellatt's book, headed "Mille-Fiore", described a broadly similar process but using the "double wall" technique (a blown sphere with the glass collapsed in on itself to form a double-walled "U-shaped" section - not just a "U" shape layer as in a modern-day "overlay cup"). When the hollow section was filled, after removal from the blowing iron, with pieces of canes and twists, and collapsed further, it could then be shaped, as Pellatt stated,
... into a tazza, paperweight, &c., at pleasure.
Pellatt showed an image of a "Venetian Ball, and another is illustrated in Jargstorf's Paperweights
, page 8, but neither provide sizes or show more than one view. From the images most people would find it hard to distinguish these from "Scramble" design weights which have canes and twists set inside a clear dome with the effect of magnification appearing to fill the dome with the canes. That's one of the problems with photos of just one view of a paperweight, or "Venetian ball" or whatever.
In fairness, I will also say that another problem with single, basic views of weights - such as in the PCC 1999 Exhibition site - is that cane details can sometimes appear to be not as described! My example of the St Louis "Boule Rouge" weight, appears to show only a few "hollow" canes with the rest having a "grey" or "greenish" centre. And even the "hollow" ones could be argued as having an orange centre. But all of the "cog" canes do have a clear centre.
Getting back to what Adam was told about "hollow" canes making Baccarat weights more special, my own view is that it would be a purely subjective issue. I don't know of any Baccarat weights that are generally regarded as "special" because they have canes that appear to be hollow - hence my original comment about this.
But I do have a "Scottish" Ink Bottle that is special (to me) because it contains an early Vasart cane with a clear ("hollow") centre which under UV light shows as Green, but all the other clear glass in the bottle shows a "modern" non-Green reaction. In this case, the "hollow" cane was very useful to my investigations into "old" Scottish canes in new pieces.