Steam engines and tractors are a prominent feature in the Pazandak photograph collection. The images, if seen in a chronological sequence, show the evolution in farm power. First, large steam engines were developed which were fairly limited in their applications. Primarily, they were used for heavy hauling, plowing, and operating a threshing machine. They soon were followed by tractors which were used for the general field work of plowing, disking, seeding, binding, as well as providing power to the threshing machine. Presented here are technical descriptions of the tractors and steam engines which appear in the Pazandak collection. For a brief history of the companies which manufactured the following tractors or steam engines, see the section entitled "Farm Machinery Companies." For a brief description of the processes or implements used with the tractors or steam engines, see the section entitled "Implements Used on the Farm."