The tome is inside a room with a model of the sun, earth and the moon rotating around eachother near the observatory. The skull is in a room in the graveyard that you need to enter doors in a specific order. Sorry i can't really be much help other than that. --- I Survived The Leak Days there were over 15000 pages of topics...it was horrifying.
In the graveyard there is a room that is full of doors, where going in one has you coming out of another. You have to have four treasure maps that depict this room in order to figure out its puzzle. Each map shows what door to enter (depicted in red) on what side of the room (the number of doors at the top of the map matches the number of doors on the side you have to enter), along with one of the Fez numbers to show the order in which to enter them. Going through these doors in the correct order will bring you to a room that has two islands floating in red water, but you will only be able to see the one you upon which you start. You have to jump into the water and swim to the other island. It has a chest with the Skull Artifact on it. --- They say money is the root of all evil... but I'm sure that problem will go away if we throw enough money at it.
Yes compared to the other artifacts which have big parts to play in the game, so far I've found no use for the Skull. --- "IF ALL ELSE FAILS USE FIRE" ~Zelda II "Sound levels can fool you." ~VirtualBoy manual