Bought a house a year and a half ago. The house is 100 years old. The subfloor is made of 8 to 10 inches wide by 2 inches thick. It is either pine or maple. The floor itself is made of planks about 4-5 inches wide by 4to 8 feet long. We have to fill the cracks but first we would like to know what to do about angling floor. We have a 4 foot high crawl space underneath. Some have recommended to lift the floor by jacking it a little every month till it is level. The angle is about one and a half inches spread over 8 feet wide on the average. It is like it is drooping more towards the corner of the living-room where the staircase (in the middle of the house) is. Give us some advice, please.

My first concern would be to find out exactly what is causing the slope. I would crawl into the crawlspace, with a bright light and a strong awl or screwdriver, and begin probing for any sign of wood damage. A house of this age is very prone to insect and water damage. Examine the whole underneath structure, including the floor joists. Examine the foundation walls for any sign of cracks or deterioration. Be very thorough since any existing problem will compound itself over the years. If you are not comfortable with this task, then, hire someone who has experience with structural problems.
There is a possibility that the cause has already been repaired but the previous owners lived with the slope. Another possibility is just poor construction that was never corrected. If everything is structurally sound, then, thoughts can be given to jacking and shoring. GOOD LUCK!!!