Alexander McKay was born at Carsphairn, in Kirkcudbrightshire, Scotland, in 1842, and was educated as part-time scholar at the village school. He came to New Zealand in 1863, landing at the Bluff from the ship “Helenslee,” and for some time he followed the occupation of a gold-miner, both in Otago and at Wakamarino, after which he went to Australia and worked on the New South Wales and Queensland diggings. In 1866 he returned to New Zealand, and for the next four years was engaged in exploring and prospecting the south-west part of the Mackenzie country, conducting his explorations alone and at all seasons of the year. It was during this period that he first became acquainted with Dr. (afterwards Sir Julius) von Haast, then Provincial Geologist for Canterbury. Later, in 1870, while engaged in prospecting for coal at Ashley Gorge, he again met Dr. von Haast, who engaged him as an assistant in prosecuting some geological surveys which he was carrying out for the New Zealand Government. After exploring the central mountain regions of Canterbury and the Shag Point coalfield the party returned to Christchurch, and Mr. McKay was further employed to collect from the saurian beds of the Waipara River, North Canterbury, for the Canterbury Museum. In 1872 he carried out the excavation of the “Moa-bone Cave “at Sumner under Dr. Haast's directions. Towards the end of that year, Dr. (later Sir James) Hector, noting the fine saurian collections in the Canterbury Museum, engaged Mr. McKay to make a collection of similar remains from Amuri Bluff for the Colonial Museum and Geological Survey. On the conclusion of this work, in March, 1873, Mr. McKay came to Wellington, and shortly afterwards was appointed a permanent officer in the Geological Survey, remaining in this employment until the suspension of the Survey in 1893. After that date he held the appointment of Mining Geologist to the Mines Department, and subsequently of Government Geologist, until his retirement from the Public Service in 1906. He died at Kelburn on the 8th July, 1917.
The geological work carried out by the Survey under Sir James Hector did not include much mapping or detailed field-work, but consisted chiefly of geological reconnaissance and exploration of unknown localities, together with reports on individual mines or small mining districts. Mr. McKay was employed at first largely in fossil-collecting; but at a later date, as his colleagues Hutton, Cox, and Park dropped out of the Survey, the greater part of the exploration fell to his share. As a fossil-collector he had a keen eye, but he had rather too high an estimation of the power of a palaeontologist to reconstruct a whole specimen from fragments, and in consequence a considerable proportion of his collections are now being found to be of doubtful utility. It was unfortunate that his collections were not examined and described at once, for with his undoubtedly great aptitude for collecting, and his memory for species, he would have been quick to acquire that special knowledge which is essential to the finest work. His collections were apparently looked over by Sir James Hector,
and a few selected specimens were displayed in the Colonial Museum under their generic names, but the great bulk were stored away and have only recently been partially re-examined. Over 120,000 fossils were acquired by the Geological Survey under Sir James Hector, and of these a considerable majority were collected by Mr. McKay. This tangible result was considered by him his greatest achievement, but it is easily outweighed by his contributions to the field and structural geology of New Zealand.
During his geological explorations Mr. McKay covered almost the whole area of New Zealand, and in accordance with the practice then in vogue he prepared reports on all his travels. These papers, published in the Reports of Geological Explorations, still form the only source of information for many districts in New Zealand. In his later years he resumed many of his earlier observations in papers dealing with larger districts, such as Central Otago, Marlborough, and the West Coast. As a writer he was not always lucid, and seldom graceful in style; indeed, his earlier papers show that writing must have been a great labour to him. He was under the further disadvantage of not being able to give a simple descriptive account of what he observed, but of having to interpret it in terms of the official classification adopted by the Survey. Nevertheless he had the merit not to suppress any discordant observations, and it is easy for one familiar with the classification adopted to obtain from the reports a clear enough account of the geological sequence he observed. As a field geologist he was a reliable worker, and in districts regarding which controversies have arisen his account has generally stood the test of time.
During the last few years of the old Geological Survey, and subsequently during his employment by the Mines Department, Mr. McKay broke frésh ground in the domain of structural geology. In 1884–85 he traversed the Middle Clarence Valley, and in 1888–89 the Awatere Valley, in each of which there are long strips of Notocene rocks resting on one side of the valley unconformably on the older rocks, and bounded by long fault-lines on the other. On each side the old rocks rise into mountains of 6,000 ft. to 9,000 ft. The presence, in the Notocene series, of the Amuri limestone, a fine-grained chalky limestone containing little or no terrigenous sediment, led Mr. McKay to conclude that at the time of its formation the Kaikoura Mountains, as such, were not in existence. Since the Notocene series is structurally involved in the mountains, he concluded that the latter originated at a comparatively recent (post-Miocene) date. His subsequent work was devoted mainly to the extension of this theory of mountain-building by block-faulting (although he did not actually use these terms) throughout the rest of New Zealand, and notably in Central Otago. Although this work received little attention at the time, it is now accepted as substantially correct by the majority of New Zealand geologists, and it is greatly to Mr. McKay's credit that he originated the idea independently of any influence from other countries.
In his later years he devoted much attention to photography, and was very successful in obtaining photomicrographs of igneous rocks, and also long-distance views of the Tararua Mountains from his home in Kelburn.