Brahmagupta's book BrahmasphutaSiddhanta dealt with a
variety of astronomical instruments. Among them, a water
clock (ghatiyantra) consisting of a bowla ghati) with a small
hole at the bottom would sink in exactly
A. 24 minutes
B. 60 minutes
C. 48 minutes
Answers
Answer:
A water clock(ghatiyantra) consisting of a hemispherical copper bowl with a small perforation at its bottom would sink in exactly 24 minutes.
Explanation:
The Water Clock :
In his monumental work Science and Civilisation in China, Joseph Needham classifies the ancient water clocks into three types:18 (i) outflow water clocks, i.e. vessels from which a certain quantity of water flows out in a specific time interval through a hole at the bottom; (ii) inflow clocks, where water from an overhead reservoir flows into a vessel and fills it in a specific time span; and (iii) sinking bowl type. In India, the first and the last type were used, not simultaneously but one after the other.
The outflow water clock used in India was called nālikā-yantra. Nālikā is a diminutive of nala, which term denotes, among others, a reed or a tube, or a hollow cylinder.19 Accordingly the nālikā-yantra must have been generally of cylindrical shape (Fig. 1). A perforation was made at the bottom of the vessel so that the water in it flowed out in twenty-four minutes or one-sixtieth part of the day-and-night (ahoratra). This span of time was also known as nālikā / nālī or nāḍikā / nāḍ
Sometime about the fifth century AD, this nālikā-yantra was replaced by the sinkingbowl type which consists of a hemispherical copper bowl with a small perforation at its bottom. When it is placed on the surface of water in a larger basin, the water enters the bowl from below through the perforation. As soon as the bowl is full, it sinks to the bottom of the basin
The weight of the bowl and the size of the perforation are so adjusted that the bowl sinks also in 24 minutes. In Sanskrit, the bowl is called ghaṭī or ghaṭikā and these two terms designate
also the duration of time measured by this device. The whole apparatus was accordingly called ghaṭī-yantra or ghaṭikā-yantra. Thus, though the nālikā-yantra and ghaṭikā-yantra designate two separate types of water clocks, the periods measured by the two are the same, viz. 1/60 part of the ahorātra, that is 24 minutes. Even after the nālikā-yantra became obsolete, the terms designating this period in the two systems of measurement, namely nālikā / nālī or nāḍikā / nāḍī and ghaṭikā / ghaṭī were used often indiscriminately as synonyms.
Reference: https://www.soas.ac.uk/ijjs/file136765.pdf