The essence of mathematical practice had multiplied in progressively refined techniques and specialization increased while the practitioners detached as well, during the eighteenth century. Mathematical instruments were the application means, and practitioners still maintained a close connection with the instrument-makers, exchanging ideas on new designs and methods. This led to an end after the 1790’s. At the same time in England, at the Royal Society, we can come across with individuals as famous as Joseph Priestley, Sir John Pringle, Benjamin Franklin, Nevil Maskelyne, Sir Joseph Banks or George Graham, Joseph Bird, Jesse Ramsden, being not the technical status an impediment to become a Fellow. The Portuguese J. H. de Magellan leads us to a case where a curious intrinsic attention on mathematical and mechanical instruments coexisted with a more general interest in science, as chemistry subjects for instance, and a strong aptitude to communicate. This mixture in just one character was not common at the time and gave place to diversified activities as getting a patent with Henry Pyefinch, the instrument-maker, on a type of barometer, to be a jury member of the mechanics section at the Society of Arts of which he was a member, to discuss modifications on barometers presented at the Royal Society, to persuade James Watt and Mathew Boulton to obtain a patent on their steam engine, to supervise the needles for the Royal Navy or the acquisition of astronomical and physics instruments for the expeditions of borders delimitations of the 1770’s in South America. In this paper we will seek to discuss why this case is interesting, the context of its development and try some conclusions.