He accompanied his brother Alexander in several of his Himalayan journeys, and was author of ‘Observations on the Spité Valley and the circumjacent Country within the Himalayas’ in ‘Asiat.
Sufficient credit has not been given to Gerard for the scientific accuracy which his assistance lent to the geographical information collected by Burnes (Journ.
His brother writes: ‘His trip to Bokhara with Colonel Sir Alexander Burnes was a mad-like expedition for him, as he had long been unwell and was obliged to leave his bed to go, and could only travel in a palkee [palanquin].
The trip killed him, for he had several attacks of fever on his way to Bokhara, and Burnes again and again urged him either to return or stop at Cabool until he recovered, but he would do neither.
… On his return he was detained three months at Meshed, and no less than eight at Herat, by fever, so that on his arrival at Subathoo his constitution was completely worn out.
At my brother's dying request I presented it to Sir Charles Metcalfe, then governor-general, from whom I received a thousand thanks.
The map is now [1840] with the army on the Indus, and … they have found the position of the roads wonderfully correct, considering the distances were estimated by time and the bearings taken with a small pocket-compass.’ Gerard died at Subathoo 31 March 1835.