Complex sentence: In 1955 the State Library obtained on indefinite loan a large collection of log books, diaries and letters left by Roe, the collection constituting one of the most important private collections ever to be lodged with the library.
Split into simpler sentences: In 1955 the State Library obtained on indefinite loan a large collection of log books, diaries and letters left by Roe. The collection constitutes one of the most important private collections ever to be lodged with the library.