Conductors and Insulators. In a conductor, electric current can flow freely, in an insulator it cannot. Metals such as copper typify conductors, while most non-metallic solids are said to be good insulators, having extremely high resistance to the flow of charge through them.onductors and Insulators. In a conductor, electric current can flow freely, in an insulator it cannot. Metals such as copper typify conductors, while most non-metallic solids are said to be good insulators, having extremely high resistance to the flow of charge through them.
Butterhead lettuce. A type of head lettuce whose botanical name is Lactuca sativa var. heirloom. Two common types are Boston and bibb lettuce. Have small, round, loosely formed heads with soft, buttery-textured leaves ranging from pale green on the outer leaves to pale yellow-green on the inner leaves.
Over the years, farmers have developed many varieties of lettuce with many forms, textures and colors. Most fall into one of four categories -- crisphead, romaine (or cos), butterhead and loose-leaf. Crisphead lettuces include the iceberg strains, favorites in the United States.e all know why Popeye the Sailor was strong to the finish, and it wasn't weight training. It was because of spinach, one of the healthiest members of the dark green vegetable subgroup.