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85/339 Mechanical calculator, adding machine, brass / steel / wood /cork, used at Sydney Observatory, probably made by Lawrence Hargrave, Sydney, New South Wales, Australia, 1880-1883. Click to enlarge.

Mechanical calculator made by Lawrence Hargrave

Probably made
Lawrence Hargrave, who later achieved fame as an aeronautical researcher, made this adding machine while working as an astronomical observer at Sydney Observatory between 1880 and 1883. He made four such machines to help him with the number-crunching part of his job, but he admitted they were unreliable due to 'imperfect workmanship'. As in some earlier machines, the keys used to input numbers operate levers underneath to turn the wheels that display the sum. In 1885 the first reliable …


Object No.


Object Statement

Mechanical calculator, adding machine, brass / steel / wood /cork, used at Sydney Observatory, probably made by Lawrence Hargrave, Sydney, New South Wales, Australia, 1880-1883

Physical Description

Calculator, mechanical, adding machine, brass / steel / wood /cork, used at Sydney Observatory, made by Lawrence Hargrave, Sydney, New South Wales, Australia, 1880-1883

Wooden base with mounted rectangular 'platform' of brass and steel. Centre portion has three rows of nine nail-like keys which act on three sprung levers pivoted behind the keyboard. Levers have geared arc which acts against gear connected to the four wheels. Wheels have cork squares painted with digits (10).



150 mm


295 mm


120 mm



This adding machine was probably designed and produced by Lawrence Hargrave during his employment at Sydney Observatory. It dates somewhere between 1880 and 1883.



Shortly after Hargrave married Margaret Preston Johnson, he commenced employment as an Extra Observer (Astronomical) at Sydney Observatory under the supervision of the Government Astronomer, H. C. Russell. On October 1, 1878 Hargrave began work and during his first three month trial earned a salary of £16-13-4 per month. In the 5 years and 2 months he spent at the Observatory (resigning on December 8, 1883), Hargrave was fortunate enough to have observed the transit of Mercury at Katoomba; the Krakatoa explosion and the transit of Venus at Mount Dromedary.

Hargrave was also responsible for conducting extensive arithmetical calculations in his role as Extra Observer. The mundane nature of this work most likely prompted him to produce this machine to make the tasks of adding simpler and quicker. According to the Abstract of Proceedings of the Royal Society of New South Wales (dated October 7, 1908), this implement was thought out by Hargrave in 1880 with four machines being made altogether. The best one was presented to the late H. C. Russell.

Two drawings of very similar adding machines, both made by Hargrave and dated 1880 (which are held by the Mitchell Library in Sydney) describe the method of operation. Hargrave writes:

"To work the machine - set it at zero by adding the complement of the number shown on the wheels, in this case 39475 + 60525 = 00000 thus, push in 6 on section A of the machine; 0 on section B of the machine; 5 on section C of the machine; 2 on section D of the machine and 5 on section E of the machine. It is best to begin at the right hand side; otherwise the dials would have shown 99995, and adding the 5 units to make it 00000 is a severe test of the workmanship. The clutch pinion is loose on the shaft in each section. Section E has not the wide and narrow 10 teeth pinions shown in the sectional elevation. Section A has not the one tooth pinion."

Despite these instructions, none of Hargrave's adding machines were reported to be reliable. In a letter to Dr H. W. MacLaurin, for example, Hargrave admits "my instrument failed through imperfect workmanship - before putting faith in any calculating machine, test it repeatedly".

This particular adding machine was transferred to the Museum of Applied Arts and Sciences from Sydney Observatory in 1985.


Credit Line

Sydney Observatory collection, 1985

Acquisition Date

24 March 1985

Cite this Object


Mechanical calculator made by Lawrence Hargrave 2021, Museum of Applied Arts & Sciences, accessed 17 October 2021, <>


{{cite web |url= |title=Mechanical calculator made by Lawrence Hargrave |author=Museum of Applied Arts & Sciences |access-date=17 October 2021 |publisher=Museum of Applied Arts & Sciences, Australia}}
This object is currently on display in Experimentations at the Powerhouse Museum.