The principle that all layers of sedimentary rock originally formed in flat horizontal layers is known as

Through careful observation over the past few centuries, geologists have discovered that the accumulation of sediments and sedimentary rocks takes place according to some important geological principles, as follows: The principle of original horizontality is that sediments accumulate in essentially horizontal layers.

True, the standard unit for volume is liters which can be represented by either a lower case "l" or a capital "l"