Editing Lothal (section)

==Science and engineering==
{{Further|Sanitation of the Indus Valley Civilization}}
[[File:Lothal bricks in drainage.jpg|thumb|A block of bricks placed in the main drainage canal with four holes, from which the net to filter out solid waste was installed]]
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.<ref name="Rao401">{{cite book
| title = Lothal
| publisher = [[Archaeological Survey of India]]
| author = S. R. Rao
| author-link = S. R. Rao
| pages = 40–41
| year = 1985
}}</ref> 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&nbsp;millimetres (0.2&nbsp;inches) thick, {{convert|15|mm|in|abbr=on}} broad and the available length is {{convert|128|mm|in|abbr=on}}, but only 27 graduations are visible over {{convert|46|mm|in|abbr=on}}, the distance between graduation lines being {{convert|1.70|mm|in|abbr=on}} (the small size indicates use for fine purposes). The sum total of ten graduations from Lothal is approximate to the ''angula'' in the ''[[Arthashastra]]''.<ref name="Rao394">{{cite book
| title = Lothal
| publisher = [[Archaeological Survey of India]]
| author = S. R. Rao
| author-link = S. R. Rao
| pages = 39–40
| year = 1985
}}</ref> The Lothal craftsmen took care to ensure durability and accuracy of stone weights by blunting edges before polishing.<ref name="Rao39">{{cite book
| title = Lothal
| publisher = [[Archaeological Survey of India]]
| author = S. R. Rao
| author-link = S. R. Rao
| page = 39
| year = 1985
}}</ref>

For their renowned draining system, Lothal engineers provided [[corbel]]led 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, {{convert|2.4|m|ft|abbr=off}} in diameter and {{convert|6.7|m|ft|abbr=off}} 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 {{convert|20|–|46|cm|in|abbr=on}} in depth, with outer dimensions of 86&nbsp;×&nbsp;68&nbsp;×&nbsp;33&nbsp;cm (34&nbsp;×&nbsp;27&nbsp;×&nbsp;13&nbsp;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 {{convert|25|mm|in|abbr=on}}.<ref name="RaoL">{{cite book
| title = Lothal
| publisher = [[Archaeological Survey of India]]
| author = S. R. Rao
| author-link = S. R. Rao
| page = 41
| year = 1985
}}</ref>