From the Wikipedia page 
The Newton Stone is an ancient pillar stone, found in Aberdeenshire, Scotland. It has been known since 1804 when the Earl of Aberdeen George Hamilton-Gordon  discovered the stone by the opening up of a new road near Pitmachie Farm, Aberdeenshire, after local shephards told him of a "curious monument" that sat there. The stone was later taken and planted in the garden of Newton House, in the Parish of Culsamond about a mile north of Pitmachie Farm by the antiquarian Alexander Gordon, alongside another stone found close by the Newton Stone at Pitmachie. George Hamilton-Gordon was indebted by the Society of Antiquaries of Scotland for writing a letter describing the original position of the Newton Stone (and the other stone) since Alexander Gordon removed them from their original position which archeologists and historians at the time thought could have been of significance. Before being moved to the garden of Newton House and subsequently becoming known as the "Newton Stone", the stone was known by locals as the "Pitmachie Stone".
The Newton Stone contains two inscriptions. The first is an Ogham script, but the second has never been identified and became known from the early 19th century as the "unknown script". The Ogham script is engraved down the left-hand side of the stone and runs across part of its face, while across the top third of the stone, roughly central, is the unknown text or unidentified script which contains 6 lines comprising 48 characters in total.
The "other" stone found with the Newton Stone at Pitmachie does not contain any inscriptions but is a Pictish symbol-stone.
John Pinkerton first published the engravings of the Newton Stone in his Inquiry into the History of Scotland (1814) yet made no attempt to decipher the unknown script. George Hamilton-Gordon's son Arthur Gordon first took these published engravings to Cambridge University in 1849 and scholars first took an interest in attempting to decipher the unknown text. Various different theories regarding the decipherment or identification of the unknown script have been proposed since 1850's.
In 1864 antiquaran Alexander Thomson read a paper to the Society of Antiquaries of Scotland addressing six claims of alleged decipherment theories of the Newton Stone:
- Phoenician (Rev. Nathan Davis)
- Celtic (Dr. Padre)
- Latin (Thomas Wright)
- Greek (Constantine Simonides)
- Egyptian Arabic (Dr. J. E Brown)
- Hebrew-Bactrian (Dr. George Moore)
There has been a certain amount of discussion on the topic since.