He was educated at a school in Bisfiop Auckland.
In 1841-1843 he published several papers on the electricity of effluent steam.
This subject he was led to study by the experience of a colliery engineman, who noticed that he received a sharp shock on exposing one hand to a jet of steam issuing from a boiler with which his other hand was in contact, and the inquiry was followed by the invention of the " hydro-electric " machine, a powerful generator of electricity, which was thought Worthy of careful investigation by Faraday.
The question of the utilization of water-power had engaged his attention even earlier, and in 1839 he invented an improved rotary water motor.
Soon afterwards he designed a hydraulic crane, which contained the germ of all the hydraulic machinery for which he and Elswick were subsequently to become famous.
This machine depended simply on the pressure of water acting directly in a cylinder on a piston, which was connected with suitable multiplying gear.
In the first example, which was erected on the quay at Newcastle in 1846, the necessary pressure was obtained from the ordinary water mains of the town; but the merits and advantages of the device soon became widely appreciated, and a demand arose for the erection of cranes in positions where the pressure afforded by the mains was insufficient.
This simple device may be looked upon as the crown of the hydraulic system, since by its various modifications the installation of hydraulic power became possible in almost any situation.
The use of steel wire for the construction of guns was one of Armstrong's early ideas.
He perceived that to coil many turns of thin wire round an inner barrel was a logical extension of the large hooped method already mentioned, and in conjunction withK.
Brunei, was preparing to put the plan to practical test when the discovery that it had already been patented caused him to abandon his intention, until about 1877.
His title became extinct, but his grand-nephew and heir, W. H. A. F. Watson-Armstrong (b, 1863), was in 1903 created Baron Armstrong of Bamburgh and Cragside.
Quotations: There is no evidence that Armstrong agonised over his decision to go into armament production. He once said: "If I thought that war would be fomented, or the interests of humanity suffer, by what I have done, I would greatly regret it. I have no such apprehension". He also said: "It is our province, as engineers to make the forces of matter obedient to the will of man; those who use the means we supply must be responsible for their legitimate application".
He was conferred with Honorary Membership of the Institution of Engineers and Shipbuilders in Scotland in 1884.
He was also an eminent scientist, inventor and philanthropist. In collaboration with the architect Richard Norman Shaw, he built Cragside in Northumberland, the first house in the world to be lit by hydroelectricity.
Armstrong married Margaret Ramshaw in 1835, and they built a house in Jesmond Dene, on the eastern edge of Newcastle.
His wife, Margaret, died in September 1893, at their house in Jesmond.