The island is "a volcanic plug of phonolite", dating to the Carboniferous period. The rock was first recognised as an igneous intrusion by James Hutton, while Hugh Miller, who visited in 1847, wrote about the Rock's geology in his book Edinburgh and its Neighbourhood, Geological and Historical: with The Geology of the Bass Rock.
The island, which has been privately owned by the Hamilton-Dalrymple family for 300 years, is a volcanic plug and stands over 100 m high in the Firth of Forth Islands Special Protection Area which covers some, but not all of the islands in the inner and outer Firth. The Bass Rock is a Site of Special Scientific Interest in its own right, due to its Gannet colony. It is sometimes called "the Ailsa Craig of the East"
It is of a similar geological form to nearby North Berwick Law, a hill on the mainland. There are a couple of related volcanic formations within nearby Edinburgh, namely Arthur's Seat and Edinburgh Rock.
Much of the island is surrounded by steep cliffs, and rocks, with a slope facing south south west, which inclines at a steep angle.
The Bass does not occupy the skyline of the Firth, quite as much as its equivalent in the Clyde, Ailsa Craig, but it can be seen from much of southern and eastern Fife, most of East Lothian, and high points in the Lothians and Borders, such as Arthur's Seat, and the Lammermuir.
The Bass is one of a small string of islands off part of the East Lothian coast, which in turn are considered some of the Islands of the Forth. To the west are Craigleith, and the Lamb, Fidra and finally to the west of Fidra, the low lying island of Eyebroughy. These are also mainly the result of volcanic activity.
To the north east, can be seen the Isle of May.
The family had from an early date a castle on the island. Sir Robert de Lawedre is mentioned by Blind Harry as a compatriot of William Wallace, and Alexander Nisbet recorded his tombstone in 1718, in the floor of the old kirk in North Berwick: "here lies Sir Robert de Lawedre, great laird of The Bass, who died May 1311". Five years later his son received that part of the island which until then had been retained by The Church because it contained the holy cell of Saint Baldred. A century on Wyntown's Cronykil relates: "In 1406 King Robert III, apprehensive of danger to his son James (afterwards James I) from the Duke of Albany, placed the youthful prince in the safe-custody of Sir Robert Lauder in his secure castle on The Bass prior to an embarkation for safer parts on the continent." Subsequently, says Tytler, "Sir Robert Lauder of The Bass was one of the few people whom King James I admitted to his confidence." In 1424 Sir Robert Lauder of The Bass, with 18 men, had a safe-conduct with a host of other noblemen, as a hostage for James I at Durham. J J Reid also mentions that "in 1424 when King James I returned from his long captivity in England, he at once consigned to the castle of The Bass, Walter Stewart, the eldest son of Murdoch Stewart, Duke of Albany, his cousin. The person who received the payments for the prisoner's support was Sir Robert Lauder", whom Tytler further describes as "a firm friend of the King".
Hector Boece offers the following description (original spelling):
to The Bass. In this period, many members of Clan MacKay ended up here, including, Neil Bhass MacKay (Niall "Bhas" MacAoidh), who gained his epithet from being imprisoned there as a fourteen year old in 1428. He was kept there as a hostage, after his father, Aonghas Dubh (Angus Dhu) of Strathnaver in Sutherland was released, as security. According to one Website
After almost 600 years, the Lauders lost The Bass during Cromwell's invasion, and the castle subsequently (in 1671) became a notorious gaol for many decades where many religious and political prisoners including Prophet Peden were sent. John Blackadder, the best known of the Covenanting martyrs, died on the Bass in 1686. He is buried at North Berwick, where a United Free Church was named after him.
The main defences are entered a little farther on in the same line, through a projecting two-story building which has some fireplaces with very simple and late mouldings. The buildings are of the local basalt, and the masonry is rough rubble; there are, as is so frequently the case, no very clear indications for dating the different parts, which were in all probability erected at different times.
A little beyond the entrance there is a tower that formed a simple bastion and to which has been added a gabled chamber in the 17th century, which, though of restricted dimensions, must have been comfortable enough, with blue Dutch tiles round its moulded fireplace, now very much decayed.
Half-way up the island stands the ruin of St Baldred's Chapel, which is sited upon a cell or cave in which this Scottish Saint spent some time. Although the Lauders held most of the Bass Rock, this part of it had remained in the ownership of The Church until 1316 when it was granted to the family. The chapel appears to have been rebuilt by the Lauder family several times. A Papal Bull dated May 6, 1493, refers to the Parish Church of the Bass, or the Chapel of St Baldred, being "noviter erecta" at that time. On the January 5, 1542 we find John Lauder, son of Sir Robert Lauder of The Bass, Knt., as "the Cardinal's Secretary" representing Cardinal David Beaton at a reconsecration of the restored and ancient St. Baldred's chapel on The Bass. In 1576 it is recorded that the Church on the Bass, and that at Auldhame (on the mainland), required no readers, doubtless something to do with the Reformation.
The natural history of the rock was written about almost five hundred years ago in John Mair's De Gestis Scotorum ("The deeds of the Scots") published in 1521. Today, the Scottish Seabird Centre at North Berwick has solar powered cameras located on the island which beam back live close up images of the seabirds to large screens on the mainland, just over a mile away. The images are sharp enough for visitors at the Scottish Seabird Centre to read the ID rings on birds' feet. The Seabird Centre has 10 cameras located on the islands of the Forth and also broadcasts the images live on the internet. The Centre also has exclusive landing rights to the island from the owner Sir Hew Hamilton-Dalrymple and operates a limited number of photographic boat trips to the islands throughout the year, weather permitting.
Due to its imposing nature, prison and connection with Scottish history, the Bass has as a result featured in a lot of fiction.
Catriona is the 1893 sequel to Kidnapped, both by Robert Louis Stevenson. They are both set in the aftermath of the Jacobite rebellion, in the mid-18th century.
The first part of the Catriona recounts the attempts of the hero - David Balfour - to gain justice for James Stewart - James of the Glens - who has been arrested and charged with complicity in the Appin Murder. David makes a statement to a lawyer, and goes on to meet Lord Prestongrange - the Lord Advocate - to press the case for James' innocence. However his attempts fail as he is once again kidnapped and confined on the Bass Rock, until the trial is over, and James condemned to death.
The book begins with a dedication to Charles Baxter, a friend of Stevenson, written in his home in Western Samoa and says:
Chapter XIV is entitled simply, The Bass, and gives a long description of the island, which is described as "just the one crag of rock, as everybody knows, but great enough to carve a city from."
In reference to the pitiful state of Tantallon Castle nearby.