Section coverage of optical and precision instruments under the Central Excise Tariff sets chapters and records no section notes. Section XVIII of the Central Excise Tariff First Schedule classifies goods under Chapters 90-92 to include optical, photographic, cinematographic, measuring, checking, precision, medical or surgical instruments and apparatus; clocks and watches; musical instruments; and their parts and accessories, with no section notes limiting or modifying that chapter-level classification.