Complex sentence: He attended the Columbia School of Mines before he joined his great uncle, James Renwick, in his architecture firm in 1878.Along with Charles William Clinton he formed the well known architecture firm of Clinton & Russell.
Split into simpler sentences: He attended the Columbia School of Mines before he joined his great uncle, James Renwick, in his architecture firm in 1878. Later, along with Charles William Clinton, William Russell formed the well known architecture firm of Clinton & Russell.