SIR CLEMENTS ROBERT MARKHAM (1830-1916)
Autograph manuscript signed headed 'Experience of ice blasting in Baffin's Bay and Barron Strait, H.M.S. "Assistance" 1850-51', describing the methods and effects of breaking up ice with explosives, 'Our blasting charges of powder were in glass bottles, earthenware jars or preserved meat tins ... When the charge was judiciously placed, and lowered so that the whole effect of the explosion was expended upon the under surface of the ice, [...] fragments were thrown up, and the sound resembled that of a very distant gun. In these circumstances the effect was most satisfactory'; giving further details and describing how they eventually escaped from the ice, 'To get out of winter quarters we marked out a channel and then rotted away the ice by strewing gravel and ashes on it. 2 and 4 lbs charges were exploded 7 or 8 feet below the ice, along the sides of the channel. It was necessary to detach an obstructing floe from the east shore of Griffith Island. With 216 lbs of powder and 32 yards of safety fuze we cleared away a space 20,000 yards long and averaging 400 broad, 3 to 5 feet thick, weighing 216,168 tons. The heaviest charge was 16 lbs lowered 10 ft below 5 feet ice. It broke up a space 400 yards square, besides splitting the floe in several directions', 4 pages, 4to, on a bifolium (small tag holes in upper corners).
The notes record Markham's experiences while serving as a midshipman on Captain Horatio Austin's Franklin search expedition of 1850-51. He extended his naval service by three years in order to take part. It was on the same expedition that the Irishman McClintock worked out the system of travelling by sledge with depots and in relays, which was thereafter adopted on polar expeditions, and which Markham regarded as the greatest achievement of the mid-19th century polar exploration.