Excellent health and the absence of any machinery for compulsory retirement kept Ellis at his post until February 1856 , when he resigned on a pension .
Excellent health and the absence of any machinery for compulsory retirement lived thirteen years more close to the museum .
Excellent health and the absence of any machinery for compulsory retirement kept Ellis at his post until February 1856 , when he resigned on a pension , and lived thirteen years more close to the museum .