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.
Butter lettuce leaves become progressively smaller toward the heart. Butter lettuce, or butterhead, is one of the four main types of annual lettuce (Lactuca sativa) widely available in the United States, along with leaf, crisphead and romaine varieties.ed-leaf varieties of butter lettuce feature leaves that are similar to green-leaf varieties but have distinctive edges, swirls or speckles of red on the foliage.