WOOD END LIGHTHOUSE, MA The originally installed optic was a 4th-order Fresnel lens. In 1916 the Lighthouse Board installed an incandescent oil vapor lamp in a 5th-order revolving Fresnel lens with 8 panels. Previously, the vapor lamp was used only in the larger 4th-order lens where heat, rising perpendicularly from the top and spreading out into a 10- to 15-degree cone, could be more readily dissipated through the top of the lens. The smaller 5th-order lens' installation was made possible by placing a metal heat deflector atop the lens to protect it from cracking. The lens was removed in 1960 when an automated modern rotating optic was installed.

http://www.lighthouse.cc/woodend/history.html

See third paragraph below 2nd picture.