In the early 1800's most grist mills used traditional methods which involved two round millstones, a grooved one on the bottom and a rotating one above it. The bottom stone was often intricately carved to get best grinding results and allow the ground flour to escape from the sides. (https://en.wikipedia.org/wiki/Gristmill)

The above stone is from the Tarrawingee Mill and is currently on display at the nearby Community centre. You can see the carved grooves for the flour to escape. A plaque nearby give some information on the stone:

"ONE OF TWO ROLLERS WHICH WAS SHIPPED
OUT FROM ENGLAND FOR SMITHS FLOUR MILL
ERECTED 1870 OPPOSITE PLOUGH HOTEL.
USED TO GRIST LOCAL WHEAT INTO FLOUR.

MILL WAS DESTROYED BY FIRE IN 1917"

Unfortunately there are some errors on this plaque. The stone is a traditional millstone, not a roller. The mill was originally a traditional stone mill. It wasn't until much later (1903) the the mill was upgraded to the newer technology roller mill. There is also evidence of the mill operating in 1866, so construction must have been earlier than 1870. Finally, the mill was destroyed in 1918, not 1917. 

Despite these minor issues, we are fortunate that the stone was preserved and donated locally.

 

An article in The Ovens and Murray Advertiser, 17 February 1866 (https://trove.nla.gov.au/newspaper/article/112907911?searchTerm=tarrawingee%20flour%20mill) mentions some details about the building and machinery at that time:

New Flour Mill.
—As it has been our invariable custom to notice the establishment of any new local industry and the erection of public buildings, mills, tanneries, breweries, &c., we paid a visit to Tarrawingee, on Monday last, for the purpose of inspecting the new flour mill, recently erected by Mr Shields at that place. The mill which is a substantial brick erection, (built by Mr Christopher Cooke of Wangaratta) is forty eight feet in length, and twenty three feet in breadth, with corrugated iron roof, and is three stories high. In outward appearance it is not unlike Messrs. Allan and Baldry's mill at Wangaratta. At the present time there are only two pairs of stones at work, but if necessary five pairs of stones can be .conveniently placed. The timber work being put up for that number. The smutting machine is one of Messrs. Robinson and Co's. patent ones' and we believe is of colonial manufacture. The ' silk dressing machine is twenty feet in length, and performs its work admirably. The stones are of the kind known as French burrs, and are manufactured by Messrs. Cochrane of London. The water required for driving the engine, is obtained from a well sixty feet deep, the supply is ample, and is conveyed to the engine by pullies, from the main shaft. Very little _ manual "labor is required in working the" mill. The engine is of 10 horse power, with double cylinder and furnished with Lowmoor boiler plate, manufactured by Messrs. Ransom and Sons, Ipswich. We understand, it is also the proprietor's intention to erect an oat meal mill, at an early date. When we visited the mill we observed a long string of teams delivering wheat; and Mr Shields informed us that his mill was going night and day.
Note that a well is mentioned for water supply, this brick lined well is still present and in use today. 
The 10 HP engine referred to would have been a steam engine, probably made by Ransomes & Sons of Ipswitch, England (https://en.wikipedia.org/wiki/Ransomes,_Sims_%26_Jefferies).
It seems like there were two pairs of millstones operating, with provision for more. It is not known if extra stones were ever added. 

New technology - Roller Mills - 1898

 In the late 1800's all around the world, older stone mills were being replaced by roller mills, which give a superior product. These roller mills were generally made of all metal and looked more industrial than the old fashioned stones. They were regularly adverted in the Australian Miller magazine, as seen from these two examples from the 1890's:
It is not known which 'patent' system was employed when Smiths converted to roller mill technology in about 1898, but it was probably to a system similar to these. At the time of the mills destruction, the ground floor carried four sets of double rollers.
In an article in the Ovens & Murray Advertiser, 27 August 1898 it is clear that the roller mills were installed by this time:

 


1899 Replaced cracked boiler

In the Ovens and Murray Advertiser of 27 May 1899 it was reported that the steam engine boiler was cracked and needed to be replaced. This was the second time a replacement was needed, and the brackish water (presumably from the on site well) was blamed.

 (https://trove.nla.gov.au/newspaper/article/199470124?searchTerm=tarrawingee%20mill%20boiler)

 


1908 More boiler problems

Another boiler issue was reported in The Albury Banner and Wodonga Express on 12 June 1908, in this case repairs were made with help from a boiler-maker form the 'metropolis' (presumably Melbourne) and the local smithy.

 (https://trove.nla.gov.au/newspaper/article/100773695?searchTerm=tarrawingee%20mill%20boiler)

 

 


Moving away from steam - 1909

Possibly as a result of ongoing issues with boiler tank integrity, around this time a decision was made to move away from steam At that time the emerging technology for heavy machine engines was gas engines, although soon both gas and steam engines were soon to decline in use in favour of electric engines.
In several of the historical references, there are mentions of moving away from steam to using a "suction gas plant". For example this from The Bacchus March Express, 11 December 1909:
A suction gas plant, costing £1,000, is being used at the Tarrawingee flour mill. Three bags of charcoal are said to do the work of one and a half cords of firewood.
 
And also an article in the Ovens & Murray Advertiser, 20 November 1909
Tarrawingee Flour Mills.
— Mr. J. Smith. J.P.. of the Anchor roller flourmills, Tarrawingee, has, with commendable enterprise, effected an important improvement in the installation of a new suction gas power plant, which has been running about a week with very satisfactory results. The plant is of a novel description, requiring only charcoal as fuel, and a contract has recently been concluded for 50 tons of this material. The plant was manufactured by the celebrated firm of Messrs. Hornsby and Sons, and is being worked at only half the power of which it is capable. The advantages of this plant, which cost £1000*, are that it is more economic than steam power,, and requires considerably less attention while working, three bags of charcoal being now used, in place of 1½ cords of firewood as formerly.
 
*Approx: A$145,000 (2020)
Interestingly, at the time of the destruction of the mill (1919), there were still 100 cords (approx 200m3) of firewood stacked next to the mill, as well as 15 tons of charcoal - presumably the wood was still used for domestic and heating purposes.
 
This engine is driven by gas, in major cities gas could be provided by a town supply, but where this was not available the partial combustion of of any material will provide the gas, so a gas producer was also needed. The one installed at Tarrawingee may have been similar to this: