Block chain may refer to:
A block chain or blockchain is a permissionless distributed database based on the bitcoin protocol that maintains a continuously growing list of data records hardened against tampering and revision, even by its operators. The initial and most widely known application of block chain technology is the public ledger of transactions for bitcoin, which has been the inspiration for similar implementations often known as altchains.
The block chain consists of blocks that hold timestamped batches of recent valid transactions. Each block includes the hash of the prior block, linking the blocks together. The linked blocks form a chain, with each additional block reinforcing those before it, thus giving the database type its name.
A block chain implementation consists of two kinds of records: transactions and blocks.
Transactions are the content to be stored in the block chain.Transactions are created by participants using the system. In the case of cryptocurrencies, a transaction is created anytime a bitcoin owner sends cryptocurrency to another.
The Lord Block is an historic commercial at 379 Lisbon Street in downtown Lewiston, Maine. Built in 1865, it is one of downtown Lewiston's oldest commercial buildings, and a reminder of the city's early commercial character. The building was listed on the National Register of Historic Places in 1986.
The Lord Block is located on the southern half of Lisbon Street, Lewiston's main business district, at the southwest corner of Lisbon and Cedar Streets. It is a 2-1/2 story masonry structure, built out of load-bearing brick with granite trim, with a front-facing gable roof that has a cross gable on the north side. The front has two virtually identical storefronts, each with a recessed entrance on the left and a plate glass display window to the right. The doors and windows are separated by rusticated granite piers, with a modern awning now extending across both storefronts and on to the adjacent building. Upper floor and side facade windows are sash windows set in rectangular openings, with granite sills and lintels. The north-facing gable is finished in decorative cut shingles, and has two window bays.