[Illustration: Cross-section, magnified 37-1/2 diameters.] [Illustration: Tangential Section, life size.] 55 BLACK LOCUST. LOCUST. YELLOW LOCUST. Yellow, from color of sap-wood. _Robinia pseudacacia_ Linnaeus. _Robinia_, in honor of Jean Robin, of France; _pseudacacia_, means false acacia. [Illustration: Habitat.] HABITAT: (See map); best on western Allegheny mountains in West Virginia. [Illustration: Leaf.] CHARACTERISTICS OF THE TREE: Height, 50'-80'; diameter, 3'-4'; bark, strikingly deeply furrowed, dark brown; prickles on small branches, grows fast, forms thickets, on account of underground shoots; leaves, 8"-14" long, pinnately compound; 7 to 9 leaflets, close at night and in rainy weather; fruit, pod 3"-4" long. APPEARANCE OF WOOD: Color, brown, sap-wood thin, yellowish; ring-porous; rings, clearly marked by 2 or 3 rows of large open ducts; grain, crooked, compact. PHYSICAL QUALITIES: Heavy (12th in this list); 45 lbs. per cu. ft.; sp. gr., 0.7333; very strong (1st in this list); elastic (9th in this list); very hard (6th in this list); shrinkage, 5 per cent.; warps badly, very durable; hard to work, tough; splits in nailing. COMMON USES: Shipbuilding, construction, "tree-nails" or pins, wagon hubs. REMARKS: Widely planted and cultivated east and west. Likely to be infested with borers. [Illustration: Radial Section, life size.] [Illustration: Cross-section, magnified 37-1/2 diameters.] [Illustration: Tangential Section, life size.] 56 MAHOGANY. _Swietenia mahagoni_ Jacquin. _Swietenia_, in honor of Dr. Gerard Van Swieten of Austria; _mahagoni_, a South American word. [Illustration: Habitat.] HABITAT: (See map); only on Florida Keys in the United States. [Illustration: Leaf.] CHARACTERISTICS OF THE TREE: Height, 40'-50'; diameter, 2' or more, foreign trees larger; immense buttresses at base of trunk; bark, thick, dark red-brown, having surface of broad, thick scales; leaves, 4"-6" long, compound, 4 pairs of leaflets; fruit, 4"-5" long, containing seeds. APPEARANCE OF WOOD: Color, red-brown, sap-wood, thin, yellow; diffuse-porous; rings, inconspicuous; grain, crooked; rays, fine and scattered, but plain. PHYSICAL QUALITIES: Heavy (14th in this list); 45 lbs. per cu. ft.; sp. gr., 0.7282; very strong (20th in this list); elastic (24th in this list); very hard (1st in this list); shrinkage, 5 per cent.; warps very little; very durable; genuine mahogany, hard to work; especially if grain is cross; somewhat brittle, and comparatively easy to split, nails with difficulty; polishes and takes glue well. COMMON USES: Chiefly for cabinet-making, furniture, interior finishes and veneers.