I hope someone here can help me.. please

Im in the process of remodeling a 140yo house and just began work on the floors. The floors had been covered up for years with linoleum in one room and overlayment and vct in others. I just finished sanding this room with a 60 grit getting ready to go back over it with finer grit but wanted to get an idea of what it was going to look like ... since i planned on just using a poly i figured wetting it a bit with a cloth would bring out the color and grain to see.

First off I havent a clue what kind of wood this is if someone could help me there i would appreciate it. But my real problem is the floor has light spots throughout it... heavier in places. Is this because of the kind of wood it is and how would i go about fixing it? I have attached 2 pics of dif areas of the floor.

thank you very much for helping!!

looks like birch. those spots are where there is still some finish on the floor. you need to drop a grit to get that floor clean.

I agree. Start with a much heavier grit. On that floor I would start with at least a 36 grit, maybe even a 24. It will clean the floors up a lot better.