OK, pics as promised...
Here's the original Hengler's Circus in West Nile St - undated, so not sure which of the various rebuilds this might be:
Here's the fantastic looking Matcham building in Wellington St - seems quite a grand building for one that was only open between 1895 and 1900, wonder how long it lasted after that?
And finally, the Sauchiehall St one - I've no great pic of the exterior, but this sketch is dated around 1901. It still says Panorama, which possibly means it dates from earlier than that - it was seemingly originally opened as a Diorama in 1882, before becoming a skating rink in 1885, then the Hippodrome from 1897 or so. A fragment of these brick arches can still be seen in the Scott St facade of the building, and the arched window in the Sauchiehall St facade looks familiar too.
Finally, this is the interior of the Hippodrome, again undated, but presumably sometime between Hubner converting it in 1897 and Hengler closing it in 1924. You can plainly see the main difference between Hippodromes and other theatres and cinemas here, namely the circular ring in front of the proscenium. This was often capable of filling with water for spectacular water-based acts, such as re-enactments of great maritime battles!
Incidentally, for further research on Hengler, go here:
http://www.theglasgowstory.com
and bang the word circus into the search engine, you'll get a few items of interest, including an undated programme for one of Hengler's shows. Also of interest is a pic of a cottage in West Nile St photographed in 1955, said to be the only remaining part of the original West Nile St Hengler's.
For further research, I'd also suggest Glasgow University Library, whose Special Collections contain a very rich archive of theatre material. Can't find anything specific on their online catalogue, but they do hold a copy of a history of Hengler's Circus published in 1981 by Sean McCarthy, published by Glasgow's Third Eye Centre, the predecessor of today's CCA next door to the Sauchiehall St building!
Gary