HMS Dido

[Observer]

I am looking at the origins of the Argo fire control system.

It is accepted generally that Arthur Hungerford Pollen became interested in gunnery control from 1900 when he happened to witness a naval gunlayer’s test near Malta, while the guest of his cousin Commander William Goodenough, then serving on the cruiser HMS Dido. Dido’s guns were firing at a range of 1,400 yards. According to Pollen’s recollections this was because “I was told that no practice was carried out at any greater range’ due to “the absence of an accurate range-finder.”

Dido was built as Eclipse-class cruiser in Glasgow 1896, and completed on 10 May 1898.

My question is, what form of rangefinder (if any) was Dido fitted with ?

It is known that the Admiralty had expressed concern about the poor accuracy of gunnery trials in 1891 (if not before) and approached Dr Barr & Dr Stroud to develop an optical range-finder based on an instrument of theirs tested by the Army at Aldershot in 1891.

According to the Barr & Stroud history ('Range & Vision') by November 1895 27 B&S Mark 1 rangefinders had been delivered to the Admiralty. By January 1896 16 B&S Mark 2 rangefinders had been supplied with 36 more on order. 50 more were ordered by the Admiralty in November 1897, and another 100 in June in1899 as the decision had been made that “every fore and aft charthouse of every capital ship” should be so fitted. A working prototype of a system to transmit information from the rangefinder to the guns was ready in July1898. The was trialed first on HMS Canopus in February 1901.