What was the original problem with the corbeled vaults?

Here are three reasons why the Civil War would be considered the first modern war:
1) Development of naval mines and torpedoes- These weapons developed by the Confederate lead to the sinking of 40 different Union ships. These weapons would be used in several different wars after this (including World War I).

2) Communication via the telegraph- The telegraph was created in 1844 by Samuel Morse. The Civil War became the first US war that used this technology. This allowed Lincoln to get much quicker updates on the war and allowed the media to report the news faster to citizens.

3) Development of the Army ambulance corp- This allowed for wounded soldiers to be recovered and treated quickly when injured in battle. This structure is still used in warfare today, as their are constantly doctors and other medical professionals nearby to help injured soldiers.