Graham, Actually I find this very very fascinating, and I will search the archives for your earlier article. I am going to be putting together a top bar observation hive this winter and perhaps make some similar observations. The observation hive I have planned is probably a bit more substantial that a standard observation hive. It will have about 10 full combs and they will be viewed from the side. It will be interesting to see how well it does. I am hoping my design is successful from a long term tenancy point of view. Scot Mc Pherson