Image from the Biodiversity Heritage Library.
Contributed by Yale Peabody Museum of Natural History.
| www.biodiversitylibrary.org
Transcription
Wednesday
Triassic and trap ridges (=basalt)
Trap = diabase or dolerite. At Orange averages 100 feet thick.
Leding 1886 speaks of it as "lava sheet"
In quarry on Mt. Pleasant avenue columnar structure is fine. O'Bourke's quarry.
Plate 9 shows radiate structure of columns. Due to irregular cooling
Undercliff quarry 1/2 miles away doesn't show fine structure.