Changing direction describing the merkle root. Its the transaction data that forms the 32 bytes of the merkle root.

ch07.asciidoc

@@ -12,7 +12,7 @@ While a block has just one parent, it can temporarily have multiple children. Ea
 
 The "previous block hash" field is inside the block header and thereby affects the _current_ block's hash. The child's own identity changes if the parent's identity changes. When the parent is modified in any way, the parent's hash changes. The parent's changed hash necessitates a change in the "previous block hash" pointer of the child. This in turn causes the child's hash to change, which requires a change in the pointer of the grandchild, which in turn changes the grandchild and so on. This cascade effect ensures that once a block has many generations following it, it cannot be changed without forcing a recalculation of all subsequent blocks. Because such a recalculation would require enormous computation, the existence of a long chain of blocks makes the blockchain's deep history immutable, a key feature of bitcoin's security. 
 
-One way to think about the blockchain is like layers in a geological formation, or glacier core sample. The surface layers may change with the seasons, or even be blown away before they have time to settle. But once you go a few inches deep, geological layers become more and more stable. By the time you look a few hundred feet down, you are looking at a snapshot of the past that has remained undisturbed for millennia or millions of years. In the blockchain, the most recent few blocks may be revised if there is a chain recalculation due to a fork. The top six blocks are like a few inches of topsoil. But once you go deeper into the blockchain, beyond 6 blocks, blocks are less and less likely to change. After 100 blocks back there is so much stability that the "coinbase" transaction, containing new bitcoin, can be spent. A few thousand blocks back (a month) and the blockchain is settled history. It will never change.  
+One way to think about the blockchain is like layers in a geological formation, or glacier core sample. The surface layers may change with the seasons, or even be blown away before they have time to settle. But once you go a few inches deep, geological layers become more and more stable. By the time you look a few hundred feet down, you are looking at a snapshot of the past that has remained undisturbed for millennia or millions of years. In the blockchain, the most recent few blocks may be revised if there is a chain recalculation due to a fork. The top six blocks are like a few inches of topsoil. But once you go deeper into the blockchain, beyond 6 blocks, blocks are less and less likely to change. After 100 blocks back there is so much stability that the "coinbase" transaction, the transaction containing newly-mined bitcoins, can be spent. A few thousand blocks back (a month) and the blockchain is settled history. It will never change.  
 
 === Structure of a Block
 
@@ -169,7 +169,7 @@ Since the merkle tree is a binary tree, it needs an even number of leaf nodes. I
 .An even number of data elements, by duplicating one data element
 image::images/MerkleTreeOdd.png["merkle_tree_odd"]
 
-The same method for constructing a tree from four transactions can be generalized to construct trees of any size. In bitcoin it is common to have several hundred to more than a thousand transactions in a single block, which are summarized in exactly the same way producing just 32-bytes of data from a single merkle root. In the diagram below, you will see a tree built from 16 transactions. Note that while the root looks bigger than the leaf nodes in the diagram, it is the exact same size, just 32 bytes. Whether there is one transaction or a hundred thousand transactions in the block, the merkle root always summarizes them into 32 bytes: 
+The same method for constructing a tree from four transactions can be generalized to construct trees of any size. In bitcoin it is common to have several hundred to more than a thousand transactions in a single block, which are summarized in exactly the same way producing just 32 bytes of data as the single merkle root. In the diagram below, you will see a tree built from 16 transactions. Note that while the root looks bigger than the leaf nodes in the diagram, it is the exact same size, just 32 bytes. Whether there is one transaction or a hundred thousand transactions in the block, the merkle root always summarizes them into 32 bytes: 
 
 [[merkle_tree_large]]
 .A Merkle Tree summarizing many data elements