page_title: Lothal
section_title: Science and engineering
hierarchical_section_title: Lothal / Civilization / Science and engineering
caption_attribution_description: bricks in drainage in Lothal (India)
context_page_description: Lothal was one of the southernmost cities of the ancient Indus Valley Civilization, located in the Bhāl region of the modern state of Gujarāt. Construction of the city began around 2200 BCE. Discovered in 1954, Lothal was excavated from 13 February 1955 to 19 May 1960 by the Archaeological Survey of India, the official Indian government agency for the preservation of ancient monuments. According to the ASI, Lothal had the world's earliest known dock, which connected the city to an ancient course of the Sabarmati river on the trade route between Harappan cities in Sindh and the peninsula of Saurashtra when the surrounding Kutch desert of today was a part of the Arabian Sea. However, this interpretation has been challenged by other archaeologists, who argue that Lothal was a comparatively small town, and that the "dock" was actually an irrigation tank. The controversy was finally settled when scientists from The National Institute of Oceonography, Goa discovered foraminifera and salt, gypsum crystals in the rectangular structure clearly indicating that sea water once filled the structure.
context_section_description: A thick ring-like shell object found with four slits each in two margins served as a compass to measure angles on plane surfaces such as housing alignments, roads or land surveys. S.R. Rao also suggested that it could have functioned as an instrument for measuring angles and perhaps the position of stars and  thus for navigation like a sextant. Lothal contributes one of three measurement scales that are integrated and linear (others found in Harappa and Mohenjodaro). An ivory scale from Lothal has the smallest-known decimal divisions in Indus civilisation. The scale is 6 millimetres (0.2 inches) thick, 15 mm (0.59 in) broad and the available length is 128 mm (5.0 in), but only 27 graduations are visible over 46 mm (1.8 in), the distance between graduation lines being 1.70 mm (0.067 in) (the small size indicates use for fine purposes). The sum total of ten graduations from Lothal is approximate to the angula in the Arthashastra. The Lothal craftsmen took care to ensure durability and accuracy of stone weights by blunting edges before polishing.
  For their renowned draining system, Lothal engineers provided corbelled roofs, and an apron of kiln-fired bricks over the brick face of the platform where the sewerage entered the cesspool. Wooden screens inserted in grooves in the side drain walls held back solid waste. The well is built of radial bricks, 2.4 metres (7.9 feet) in diameter and 6.7 metres (22 feet) deep. It had an immaculate network of underground drains, silting chambers and cesspools, and inspection chambers for solid waste. The extent of drains provided archaeologists with many clues regarding the layout of streets, organisation of housing and baths. On average, the main sewer is 20–46 cm (7.9–18.1 in) in depth, with outer dimensions of 86 × 68 × 33 cm (34 × 27 × 13 in). Lothal brick-makers used a logical approach in manufacture of bricks, designed with care in regards to thickness of structures. They were used as headers and stretchers in same and alternate layers. Archaeologists estimate that in most cases, the bricks were in ratio 1:0.5:0.25 on three sides, in dimensions which were integral multiples of large graduations of Lothal scale of 25 mm (0.98 in).
caption: A block of bricks placed in the main drainage canal with four holes, from which the net to filter out solid waste was installed
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