on 22 July with 450 captives. She arrived at Grenada on 1 October. She left for Bristol on 6 November, and arrived there on 12 February 1789. Brothers had left Bristol with 38 crew members. She arrived at Grenada with 27 of her original crew, and discharged three there; she also enlisted one man. Five men died on the homeward voyage, and she discharged four at Kinsale in January 1789. She arrived back at Bristol with 16 crew members. This voyage and the subsequent ones took place under the provisions of Dolben's Act. Dolben's Act limited the number of enslaved people that British slave ships were allowed to carry without penalty, based on the ships' tons burthen. It was the first British legislation passed to regulate shipping of captives. In 1788–1789, James Jones, Thomass owner, had nine enslaving vessels at sea or on the coast of Africa. He estimated that the Act reduced the number of captives his vessels were allowed to carry by a number equivalent to 23% of the pre-Act total. For Brothers, the estimate was a reduction of 84 captives, from 400 to 316, or 21%. Jones was using 190 tons as the basis for his estimate. For Brothers the cap would have been 334 at a burthen of 200 tons, or 336 at a burthen of 201 tons. 3rd enslaving voyage (1789–1790): Captain David Williams sailed from Bristol on 22 July 1789. Brothers arrived at Cape Coast Castle on 5 September, and acquired captives at New Calabar. She arrived at St Vincent on 1 February 1790 with 310 captives. She sailed for Bristol on 22 March and arrived there on 7 May. Brothers had left Bristol with 34 crew members. One man enlisted while she was on the African coast. She arrived at St Vincent with 24 crew members and discharged 11 there. She enlisted eight men before sailing. She returned to Bristol with 21 crew members. Dolben's Act also provided for bonuses for master and surgeon for low mortality among the captives carried. Masters received a bonus of £100 if the mortality rate was under 2%; the ship's surgeon received £50. For a mortality rate between two and three percent, the bonus was halved. There was no bonus if mortality exceeded 3%. Dolben's Act apparently resulted in some reduction in the numbers of slaves carried per vessel, and possibly in mortality. 4th enslaving voyage (1791):