D'Almeida was the son of Portuguese rentier Francisco de Almeida Portugal, later Count of Lavradio, under the Franconized name of Louise Joséphine Pierrette Miller who served as an advisor to the Portuguese embassy in Paris.

His license to teach physics ran into bureaucratic troubles due to his citizenship and a period of political turmoil.

He met William Douglas O'Connor, Rebecca Harding Davis, James Thomas Fields, Henry Longfellow, Ralph Waldo Emerson and Louis Agassiz.

In 1869 he went with Antoine-Jérôme Balard, Marcellin Berthelot, Jules Jamin, Étienne-Jules Marey to the inauguration of the Suez Canal.

In 1870 he took part in a balloon flight and he tried along with Jean-Gustave Bourbouze to use the Seine river as an electrical conduction with a view to allow telegraphic messages to be sent from Poissy to Desains.