In his Breve discurso de los descubrimientos de America Martinez says that he saw in his voyage of 1774 with Juan Perez, a wide entrance about 48° 30′, which he considered to be, either the strait of Juan de Fuca, or of Aguilar, which ought in his opinion to connect with Hudson's Bay.
Campos in his Espana en California, page 4, adds that Martinez on his return from Nootka in 1789, said that the pilot Narvaez had "encontrado de nuevo" the strait of Juan de Fuca.
In Humboldt's Essai Politique sur le Royaume de la Nouvelle-Espagne, volume 2, page 489, after speaking of Malaspina's wish to examine the coast beyond Nootka, he says:
Le vice-roi, doué d'un esprit actif et entreprenant, céda d'autant plus facilement a ce désir, que de nouveaux renseignemens donnés par des officiers stationnés a Noutka sembloient rendre probable l'existence d'un canal dont on attribuoit la découverte au pilote grec Juan de Fuca, depuis la fin du seizieme siecle. En effet, Martinez, en 1774, avoit reconnu tine entree tres-large sous les 48° 20′ de latitude. Le pilote de la goelette Gertrudis, l'enseigne Don Manuel Quimper, qui commandoit la bélandre la Princesse Royale, et, en 1791, le capitaine Elisa, avoient visté successivement cette entrée; ils y avoient meme découvert des ports surs et spacieux.
As far as I can ascertain these are the only references to this strait having been seen by the Spaniards prior to 1790. It will be noticed that Humboldt's statement, which is the latest in point of time, is the strongest. The Viage, which was an official publication by the Spanish Government, says that in 1774 Martinez "thought he saw"; then Martinez himself says that in 1774 "he saw"; and lastly Humboldt says that he "avoit reconnu", the strait of Fuca. It is certainly worthy of remark that if the pilot, as Martinez was in 1774, really saw the strait so long looked for, and not simply "thought he saw" it—whatever that may mean,—he did not, as his duty was, report the fact to the commander of the expedition, Juan Perez.