Henry Carter Galpin was the eldest son of the country gentleman, artist and political cartoonist Thomas Carter Galpin. He was apprenticed to his uncle, architect Joseph Galpin, who provided him with comprehensive training. However, Henry also showed an early interest in mechanics and constucted several unusual clocks. After working with his uncle for some years he joined the staff of the civil engineer Sir John MacNeill and was sent to Ireland where he took part in surveying for the Great Southern and Western Railway during the mid-1840s. His health was affected by long hours in the Irish bogs and while convalescing he spent a year working with a skilled watchmaker in London to enable him to follow a less strenuous career. In September 1848 he left for the Cape Colony to further recuperate in its sunny climate. He married Georgina Maria Luck in Cape Town in 1850 and settled in Grahamstown where he practised as a watchmaker and jeweller to his death in 1886. The couple had seven sons, including the botanist E.E. Galpin*.
In 1859 Henry purchased a double-storeyed building in Bathurst Street which became his home and business premises. Around 1870 he extended the building and some ten years later, with the help of his son Walter, planned and made further additions. These included a meridian room, a small observatory above it, a clock tower, and a camera obscura. The meridian room was used mainly to observe the meridian passage of the sun, an image of which was projected by a small hole near the ceiling onto the floor. On the floor Galpin had drawn a curve indicating the equation of time as a function of the sun's meridian altitude, so that he could determine local mean solar time. In the observatory, fitted with four folding doors, he had a 216 mm reflector. The camara obscura, Walter's great interest, provided a panoramic view of the town, projected on a horizontal surface in the observatory, and attracted many visitors. He also had a large pendulum clock constructed in 1883, which he installed in his house. It was a smaller version of one that had recently been completed for the Royal Courts of Justice in London, and was fitted with an early example of a temperature compensating pendulum composed of zinc and iron tubes. The clock was regulated by Galpin's meridian observations and set to show Grahamstown mean solar time. In his advertissements in a local paper Galpin referred to his premises as The Observatory.
After his death the business and building were taken over by his sons as Galpin Brothers. The building was later restored and turned into a museum. A copy of Galpin's manuscript describing his voyage to the Cape in 1848 is in the Strange Collection of the Johannesburg Public Library. A copy of his memorandum book, with lists of items ordered for his store and observatory, is in the Albany Museum.