A slip (also sometimes called a scoop, scraper, or road scraper) was the common implement for moving dirt when doing such things as digging ponds or making fills where large volumes of dirt were needed.
RIO GRANDE. The Rio Grande rises in Rio Grande National Forest, San Juan County, Colorado (at 37Â°47' N, 107Â°32' W), as a clear, spring and snow-fed mountain stream 12,000 feet above sea level. Its origin is at the Continental Divide in the San Juan Mountains.
Setting the Rio Grande river as the southern border would begin the boundary from the Continental Divide West, 10 miles east of present day Silverton, Colorado and follow the course of the river as it flows southward through what is the present day States of New Mexico and Texas and finally out to the Gulf of Mexico.