Spirit level by W. Ottway & Company of Ealing, London, in box, early 20th century

Spirit level made by W Ottway & Company of Ealing, London. Basically a telescope that can be set on a tripod, this instrument would be mounted horizontally on a marked spot. When rotated, it would be possible to measure small changes in height, with the aid of an assistant with a measuring rod walking around the plot to be measured. This would be useful in road, rail and canal building, as well as landscape gardening.