So whose razor-sharp mind has the edge?

Today, we conclude our series with two of the more modern innovations credited to Scots - ultrasound scanning systems pioneered by Ian Donald and James Goodfellow's work in developing the cash machine and pin number system.

So, do you select one of these contemporary pioneers - or do the theories of James Clerk Maxwell and Lord Kelvin win hands down for you? Or will you select one of the "big names" of the inventing world - such as James Watt, with his crucial refinements of the steam engine, John Logie Baird, with his work on developing television, or Alexander Graham Bell with his telecoms.

Perhaps you will look instead to Alexander Fleming's "lucky" discovery of penicillin, James "Young" Simpson and his chloroform dinner party, following which he helped ease the pain of childbirth, or "Paraffin" Young, whose work transformed the physical landscape of Scotland?

All these pioneers have helped to develop Scotland's enormous worldwide reputation for engineering, science and medicine. We hope our articles this week have helped you to find out more about these inventors - and to decide which one made the greatest contribution.

You have until next Wednesday to cast your vote and we will announce the winner towards the end of next week.

If you have voted already, thanks very much - if not, then what are you waiting for?

PROFESSOR IAN DONALD

Born: December 1910, Cornwall

Died: 19 June, 1987, Glasgow

Claim to fame: Developed the use of ultrasound in pregnancy

THE Regius Professor of Midwifery at the University of Glasgow was known as "Mad Donald" by his colleagues, but his work transformed obstetrics and gynaecology.

A war hero who had rescued wounded airmen from a burning aircraft, Ian Donald had become fascinated by gadgetry, particularly sonar and radar during the war.

Donald was convinced that ultrasound would become a useful tool for measuring growth and checking for abnormalities in the womb.

At the time, sonar was mostly in use by the Royal Navy, but Donald believed that the technique could become an invaluable tool for gynaecologists.

Donald's post-war research, into the breathing problems suffered by some newborn children had already led him to invent a device to help infants who had respiratory difficulties.

In 1954, he was appointed to the chair of midwifery at Glasgow University, where the proximity of the shipbuilding yards gave him access to engineers who understood the science of sonar.

Donald teamed up with the shipping engineer Tom Brown and, after testing the prototype device on cysts, tumours and lumps of steak, they developed the world's first B-type scanner, which was put to use on a number of willing expectant mothers in Glasgow.

In 1958, after successfully detecting an ovarian cyst in a woman who had been diagnosed as having inoperable cancer of the stomach, Donald contributed a paper to the Lancet, outlining the breakthrough he had made.

"From that point," he said, "there was no turning back."

Later, Donald wrote that the great advantage of ultrasound was that it could be administered without any discomfort or loss of dignity to the patient.

He said dissatisfaction with the existing methods of examining women in pregnancy had led him to persevere with the new technique.

"Anyone who is satisfied with his diagnostic ability and with his surgical results is unlikely to contribute much to the launching of a new medical science," he said. "He should first be consumed with a divine discontent with things as they are.

"It greatly helps, of course, to have the right idea at the right time and quite good ideas may come, Archemedes' fashion, in one's bath."

In 1959, Donald noticed that clear echoes could be detected from the head of a baby in the womb and he began perfecting a method of measuring the growth of an unborn child using the results.

Over the next few years, he and his team developed techniques for studying different stages of pregnancy and for detecting potentially life-threatening conditions in the womb.

While most ultrasound equipment is now manufactured in Japan, the early work of Ian Donald and Tom Brown was crucial in establishing the use of the technique in pregnancy.

JAMES GOODFELLOW

Born: Paisley, 1937

Claim to fame: Inventor of the Automated Teller Machine (ATM) and Chip and PIN

IT SEEMS strange to think of it now, but it was pressure from the trade unions which led to the invention of automatic banking.

James Goodfellow, a Scottish engineer who worked for Smiths Industries, was given the project of finding a secure way for people to access their money when the banks were closed.

Trade unions were putting pressure on the big banks to give tellers Saturday mornings off, so they too could go shopping at the weekends and spend their wages.

Today, there are 1.25 million cash machines worldwide, but it was Goodfellow who came up with the idea of a four-digit PIN which would allow people to access their cash.

The range of 0000 - 9999 means there are a possible 10,000 combinations of numbers.

Most PIN machines only allow three attempts before the card is blocked and access to the cash is prevented.

Goodfellow said: "We considered lots of different systems based on retinal scans and fingerprints, as well as voice-recognition machines, but they weren't technically feasible at the time."

The idea for the four-figure code meant people would be able to access their cash, but only if they punched in the correct four-digit number.

"There was an arithmetical relationship between that number and the number encoded on the card by means of a series of binary codes. If the two numbers matched up, you got your money. The idea was that if you alone knew the PIN, there could be no fraud."

Goodfellow patented his invention in 1964 and the basic ATM design is still in use today.

Like many other innovators, Goodfellow has been dogged by claims that others invented the ATM, notably by a fellow Scot, John Shepherd Barron, who invented an ATM which used a radioactive strip.

Nonetheless, Goodfellow is the man responsible for the four-figure access code which has become such a ubiquitous part of modern life.

"Among my friends and family, [the ATM] is known as Jim's money machine," he said.