Ka cika wannan magana: Da yake ya koyi game da sinadarin quinine a Landan, Castro Sarmento ya ƙirƙiro wani magani da ake kira Água de Inglaterra, wanda ya zama sananne a ƙasar Portugal inda zazzabin cizon sauro har ila yake da yawa a kudancin ƙasar. A shekara ta 1731 ya tsara wani shiri na lambun tsirrai a Coimbra. Castro Sarmento ya yi rubutu tare da malamai da yawa, a tsakanin wasu tare da Farfesa João Mendes Sachetti Barbosa na Lisbon, wanda ya ba shi labarin mummunan
girgizar kasa da ta lalata babban birnin Portugal a 1755, kuma tare da Jesuit B. Soares, wanda ya sanar da shi abubuwan da ya lura da su a cikin mulkin mallaka na Portugal na Brazil. Ya kasance mai goyon bayan Newtonianism kuma ya yi ƙoƙari ya haɗa shi da ilimin tauhidi na Yahudawa. Ya wallafa "Theorica verdadeira das marés, conforme à philosophia do incomparable cavalhero Isaac Newton" (Treatise on the true theory of tides, according to the philosophy of the incomparable gentleman Isaac Newton), littafi na farko a cikin Fotigal don ba da shawara ga ra'ayoyin Newton (London, 1737).