How did Johannes Hevelius' long telescope work? Why all the round holes? The drawing below, found in Wikimedia and at lib.harvard.edu is of a very long tubed aerial telescope. I believe it is taken from his 1673 work Machinae coelestis.

I've always wondered about the purposes of all those (20+) square blocks with round holes, spaced evenly from one end to the other.

I've included two cropped views from Harvard University, Houghton Library, pga_typ_620_73_451_fig_aa (found here) the first of which I've zoomed and enhanced the contrast both to better appreciate the cute bird, and to try to read the annotations; there seems to be a 772 or 722 next to one of the blocks near the top left.

Question: What was the function of all of these blocks? Is it optical, or mechanical, both, neither? When I was young I thought there were lenses in each one, but I'm assuming now that at least the central circular holes are completely open.

I think it is pretty easy to guess either one, but presumably with such detailed annotation there is text to go along with this image somewhere and it is likely that we can know Hevelius's intention. I just don't know where to read the text. 

I believe that the text is here but it's 1,000 pages long and in a language that I can't understand.
In general,  the less the support structure weighs, the easier it is to move the whole thing around.  Home-user telescopes usually have a solid body because it's by far the cheapest and simplest way to get a small rigid structure.

Large observatory 'scopes often have a minimal framework supporting the secondary (the far element in a reflector);  here the primary refractor is supported with a similar structure.

Most certainly the support blocks do not contain lenses.  For one thing, just imagine trying to align and focus a 12 or 15-element system!  For another, producing the lenses for telescopes of that size was incredibly tedious back then (and now, really).  

There are a couple great chapters in "The Age Of Wonder" by Richard Holmes about a couple of the early astronomers &amp; scope builders in Great Britain for those who are interested.