Tiers of shining casements

Tiers of shining casements
 

http://www.freeenglish.jp/holmes/en/redc-en-006.html
The light had suddenly gone out, the glimmering square of window had disappeared, and the third floor formed a dark band round the lofty building, with its tiers of shining casements.

========
My interpretation:
-The third floor is dark, but other floors contain casements (=windows), which are shining because people there are using lamps.

Do you agree?

The only light on the third floor had gone out. The other floors are still lit, hence the shining casements on those floors.

Thank you~