For several years the staff of the Agricultural Engineering Section of the Iowa Experiment Station has been making careful investigations concerning modern silo construction and the success and merits of each type now in use. The results of these investigations were first published in Bulletin 100, which was distributed in July, 1908. The demand for this bulletin was so large, not only from Iowa, but from other states, that a second edition was published in July, 1909. This bulletin treated of all the types of silo construction then in common use.