Here's a short story:

Starting in the coal mines, by the mid-19th century elevators were operated with steam power and were used for moving goods in bulk in mines and factories. These steam driven devices were soon being applied to a diverse set of purposes - in 1823, two architects working in London, Burton and Hormer, built and operated a novel tourist attraction, which they called the "ascending room". It elevated paying customers to a considerable height in the center of London, allowing them a magnificent panoramic view of downtown. 

The hydraulic crane was invented by Sir William Armstrong in 1846, primarily for use at the Tyneside docks for loading cargo. These quickly supplanted the earlier steam driven elevators: exploiting Pascal's law, they provided a much greater force. A water pump supplied a variable level of water pressure to a plunger encased inside a vertical cylinder, allowing the level of the platform (carrying a heavy load) to be raised and lowered. Counterweights and balances were also used to increase the lifting power of the apparatus. (End of story)

Provide your best guess for the following question. Give ONLY the guess, no other words or explanation.

For example:

Guess: <most likely guess, as short as possible; not a complete sentence, just the guess!>

Here are a few examples of questions and answers:

Question: How were goods moved?
Guess: elevators

Question: driven by what?
Guess: steam

Question: What attracted tourists?
Guess: Ascending Room

Question: Where was it built?
Guess: London

Question: When was it built?
Guess: 1823

Question: By whom?
Guess: Burton and Hormer

Question: What did Armstrong build?
Guess: hydraulic crane

Question: In what year?
Guess: 1846

Question: What was the primary purpose?
Guess: Loading Cargo

Question: Where were the elevators used?
Guess: mines and factories

Question: Was the crane a success?
Guess: yes

Question: What did it replace?
Guess: steam driven elevators:

Question: Why were they successful?
Guess: they provided a much greater force

Now answer the following question in the same format.

Question: What  increased the lift power?

Counterweights