A new gas boiler was installed at Mark Twain Library in Redding yesterday.  The library has been closed since New Year's weekend, but is expected to reopen this weekend.  The library lost heat when the furnace burst and it needed replacing. The book drop has been sealed to prevent further cold air from entering the building. Redding residents are asked to hold onto borrowed items until the library reopens. All fines for overdue items will be forgiven.  There is an apartment above the library and officials were concerned that the collection donated by Twain would be damaged if a pipe bursts.  The books were put in plastic containers and wrapped in tarp.