IN a recent book review and a reader's letter there was a difference of opinion about when the first powered vehicle appeared on Scottish roads. One suggestion was 1860, when the Earl of Caithness's steam carriage made its epic journey over the Ord and Berriedale. That was outbid by an 1833 reference to a similar vehicle in Aberdeen.

The story actually starts a few years earlier still, although Scotland was much slower than France and England in producing its first self-propelled road vehicle. In the autumn of 1828 young James Nasmyth, later famous as inventor of the steam hammer and the steam pile-driver, built a steam carriage at Edinburgh which, he recalled in later life, ``ran many a mile with eight persons in it''.

But the real pioneer here was David Napier. In 1827 he started a steam carriage service in Argyll. Passengers could sail on one of his steamships to Kilmun, transfer to the steam carriage for the drive to Loch Eck, sail up the loch on his little iron-built steamboat the Aglaia, take a horse-drawn coach to Strachur, and continue by steamer to Inveraray.

Napier admitted he had problems: ``From the softness and the hilliness of the roads, and more particularly from the want of knowledge how to make a boiler, we could not obtain the speed I expected.''

In the following decade, the most successful steam carriage service in Britain operated hourly between Glasgow and Paisley. It started in 1834 with six 26-passenger vehicles designed by John Scott Russell, one of several Scottish engineers in this field. Unpopular with the people responsible for maintaining the road, the heavy steam coaches certainly did damage to surfaces built for lighter horse traffic.

One day, a pile of loose stones was left across the Paisley road. In trying to cross it, the next steam carriage to come along burst its boiler. The explosion killed or injured all the occupants. The road trustees admitted responsibility and the service was abandoned. Parts of the blown-up carriage still survive as a relic in the Museum of Transport in Glasgow.

Victorian legislation re-stricted the running of steam road carriages in Britain. But one successful design of the 1870s was patented by Robert Thomson, the Scots engineer more often remembered as original inventor of the pneumatic tyre.

Around the turn of the century the US and France were the main centres of steam-car manufacture. In America, Stanley and White were well regarded, while by 1902 there were more Locomobile cars on the road than any other make, all steam-powered.

Diversifying in 1873 from the family business of bell-founding, Amedee Bollee of Le Mans was a prominent steam-car manufacturer in France, but Leon Serpollet showed steam's real performance potential. He was financed by an American called Gardner, and a Gardner-Serpollet defeated all opposition at the 1902 Bexhill speed trials in Sussex. Another set fastest time at the Nemphlar hill climb near Lanark.

Serpollet's greatest success also came in 1902, with a new world land speed record of 75mph. Four years later, Fred Marriott managed 121mph with the low-slung Stanley Rocket at Daytona Beach.

Scottish-built steamers of that time were rather more mundane. The oldest to survive in roadworthy condition is the three-wheeled Craigievar Express of 1897. Simply a one-off, and far more basic than contemporary steam cars intended for the market, it was built by the inventive Andrew Lawson, a postman whose run included Craigievar Castle.

The Express is now the pride of the Grampian Transport Museum at Alford. Currently having its boiler replaced, it has three public outings scheduled for its centenary year.

John Simpson of Stirling produced several steam cars up to 1904. Halley built a steam lorry before deciding to concentrate on petrol engines. But the Sentinel steam wagon was one of the great heavy-haulage vehicles of the first part of the century, built at Polmadie in Glasgow until 1915, when pro- duction moved to Shrewsbury.

Transport historian Robert Grieves has researched several steam bus services. One was started in 1907 between Stranraer and Drummore, using Darracq-Serpollet chassis with bodywork by the Glasgow and South Western Railway workshops at Kilmarnock! Just before that, Morton's of Wishaw used a steam bus on the Newmains route. Another Edwardian service in Berwickshire was by Stanley steam cars running between Reston railway station and Coldingham.

Only a few steam car makes survived World War I. There is a fine Stanley, for example, in the Glasgow Museum of Transport. The rare but magnificent Doble from California continued in production until 1932. It could be on the move, with a full head of steam, in a minute and a half from a cold start, and had a range of 1500 miles.

Abner Doble reckoned it would outpace anything on American roads apart from a Lincoln, and it could ``hold'' a Lincoln anyway. But his cars were expensive - on a par with Rolls-Royce.

The most unlikely steam vehicle of them all was the Travelair biplane demonstrated by the Besler brothers in 1933 at San Francisco. One account described its landing technique: ``The pilot uses the well-known characteristic of the steam engine - he reverses his motor and propellor while in the air and thus is enabled to bring his ship to a full stop within a few feet after the landing wheels touch the ground.''

Reverse thrust, in other words, before the era of the jet.