This blogspot sets out to record photographically and by location, a range of the surveyor's  Bench Marks which can still be found around the Island of Ireland. 

During the 19th century a very extensive and detailed mapping of the whole of Ireland took place. This work was undertaken by a team from the British Ordnance Survey Office. 
The first part of this work took place between 1827 and 1842 when Ireland was surveyed and maps of the country produced (1906 map sheets in all) at a scale of 6 inches to the mile. During the 1850s and 1860s revision work was carried to bring the maps up-to date and correct some errors. In 1888 new survey work commenced which mapped Ireland at a much more detailed scale ie 25 inches to the mile. The maps produced were considered to be of a very high quality and unequalled for any other part of the world at that time. 
At the present time copies of these maps are still available but technology has moved on and current mapping uses remote sensing digital technologies combined with GPS to produce maps of a very different nature and with extreme accuracy. 
However there remains, distributed around the island, a very tangible, if sometimes obscure physical evidence of the original mapping of the 19th century. This refers to the benchmarks which were an integral part of the original mapping process and which still today can be found at many locations.
The term benchmark (sometimes written bench mark) refers to a short horizontal line, approx. 8 cm in length, with an arrow below the line, pointing to a precise point on the line, as shown here.

The mark was made by surveyors chiselling the lines onto solid smooth rock surfaces. The location chosen was usually a very permanent feature such as a bridge, house wall, pillar, monument, church, foundation plinth or other structure which had a permanence in its environment. The normal positioning of the bench marks was close to the ground. The precise height of the horizontal line was established, using levelling techniques, to the nearest benchmark already in position and ultimately to the original ordnance datum (mean sea-level) used in setting up the surveying network. The sea-level datum used for the survey was the low water mark (on Poolbeg Lighthouse) at a spring tide on 8th April 1837. But in 1959 this was replaced by what was considered to be more accurate datum. After 10 years of measurements the new ordnance datum (OD Ireland) was taken as the average sea-level at a point at Malin Head in County Donegal.

The geographical height and location of each bench mark can be found on the 25inch maps finalized in the 19th century. Many thousands of these marks were made during this work. A bench mark in a neighbourhood was often referred as a crow's foot, and often had a certain status there.
With the passage of time many of the bench marks have disappeared due to road widening, demolition/redevelopment of old buildings, changes in the height of surrounding surfaces and natural erosion.
The author hopes to record at least two bench marks in each of the 32 counties of Ireland, keeping the total number of recordings to approx. 100. For each location a photographic record wil be published here. Also given will be the geographical location of the site as well as some notes relating to historical connections, unusual attributes or any other matter which the author considers to be of interest. 
The blogsite will be arranged in county order (alphabetical order within a provincial structure).

Ulster.


Antrim
Armagh



Cavan
A particularly interesting form of benchmark is to be found on Sliabh Cuilcagh which is a peak which straddles the Irish border. Counties Cavan and Fermanagh meet here and it is the only cross-border county top, being the highest point in each county. Its height is 665 metres (2,181 ft). The bench mark is inserted into the side of a trigonometrical pillar (trig point). It also carries a number, 2076. These concrete pillars are of a later date, most being erected in the mid 20th century. This mountain summit was one of the triangulation points used in the first OS survey. In fact the distance between it and another triangulation point at Keeper Hill was the longest distance used in any of the triangulations.


Derry.

Donegal.

Down.

Fermanagh.

Monaghan.

Tyrone.


Connacht. 

Galway.

My first benchmark to be recorded in Connacht is in county Galway. It is halfway along the green route known as An Seanbothar, which links Clonbur ( An Fhairce) with Cornamona. 






Approx 3 km south of the village of Williamstown a bench mark can be seen at the corner of a farm shed, in the townland of  Liskea, spot height 279.0 ft.

To the north of Williamstown, on the Ballinlough road at Briarfort a bench mark is cut into the bottom of a  pillar of what was in the past Lettera School.  The spot height here is 282.6 ft.






Leitrim. The river Shannon flows through the county town of Carrick-on-Shannon. This is a very important crossong point on the Shannon and a benchmark can be seen on the northern wall in the center of the bridge. It has been chiselled out underneath a plack which commemorates the building of the bridge in 1846. The inscription reads: This bridge was erected by the commissioners for the improvement of the navigation of the river Shannon   1846. The spot height for the BM is 163.1 ft.
On the Eastern bank of the river is another interesting historical feature. A small fragment of Carrick-on-Shannon castle. 
A commemorative inscription nearby can easily be read:

 Mayo.
Claremorris has a very fine building which acts as a Library but was in the past the local Church of Ireland.

A bench mark can be seen at the right hand side of the westerly facing entrance door.

 The spot height is 236.8 feet. 




At the North end of the tower of the Old Church at Knock can be seen a benchmark which has been highlighted with white paint. 


The spot height of this bench mark is 332.5 feet. 

Sligo.

Drumcliff is a small town north of the city of Sligo. Here is to be found the grave of 
WB Yates. On the front door step of the nearby Saint Columba's Church can be found a most unusual bench mark, it has been inscribed horizontally (flat) on the stone. The spot height is 48.4 feet as listed on the 25inch map. 





 Leinster.
Dublin.

This bench marks is situated on the base of an entrance pillar in the townland of Richardstown, North-county Dublin.

Heuston Station (formerly Kingsbridge station)  is one of the iconic buildings in Dublin. As one faces the front facade a bench mark can be seen on the South side (left handside), as shown below.

The bench mark is on the first corner block nearest the lefthand metal post. This bench mark is not listed on the historic 25 inch map, but this map carries a BM on the nearby Liffey bridge with a spot height of 29.2 ft. This BM can be easily seen on the granite bridge section seen below.
In Dublin city center, at 9/10 Talbot Street a BM can be seen at the base of a rather ornate building. The spot height here is 23.5 ft.




LONGFORD.
The Royal canal interacts with the Shannon waterway at Cloondara at county Longford. It is alos the place where the western end of the Royal Canal Greenway starts. There is a broad harbour here  Richmond Basin. The following photos show the location of a bench mark (horizontally cut) aon the wall of lock 46. The spot-height is 141.4 feet.


Careful inspection of this photo shows the bench mark at the canal edge of the large center wallstone.
There are not many such flat (horizontal) bench marks to be found in Ireland. 










Munster.

Cork. 
This is the largest county in Ireland so it certainly contains a large number of existing bench marks.
The first of these to be recorded by the author was in St Matthew's Church at Baltimore.

Plaque in the front gate-pillar of the church.




The bench mark in the south-western corner of the church. Unusually it has a metal spike 
driven into the central point of the mark.



Baltimore, (Dun na Sead in gaelic) is a small seaside town in coastal, mid-county Cork. It is most famous for the 'Sack of Baltimore' which was carried out by Barbary Coast pirates in June 1631. More than 100 people were taken away, most never to return to Ireland again. It is the only recorded raid by so called corsairs on the Irish coast.

The next Cork bench mark is to be found in a very different type of location: The A-Block at Spike Island/Fort Mitchel, the star shaped fortress which is the dominating feature of the historic island in Cork harbor. The island has been an early Christian monastic site, a British island fortress, a prison and is currently one of the most visited tourist attractions in Ireland.





Spot height 104.7 feet.

St Peter's church in North Main St, Cork city is a very historic building dating back to the 12th century. In the late 1900s it became derelict but recently has been refurbished and is now a very attractive cultural center. Visitors to the building cannot but notice, at the left hand side of the building a bench mark.





Of particular interest is the fact that this bench mark does not appear on the 6inch or 25inch maps of Cork City.
Bridges feature prominently as locations for bench marks. The bridges at the western and eastern side of Midleton's main street each carry bench marks, 2 pictures below. 



Bridge over the Owenacurra river on the Western side of Midleton, can you spot the bench mark? 
The spot height here is 32.8 ft.

Bridge over the Dungourney river at the Eastern side of Midleton. The spot height is 23.0 ft.

Elizabeth Fort was a very important defensive fort and can be found off Barrack street in Cork city. Originally built in 1601 is was besieged by Williamite forces in 1690 and captured from Jacobite forces. It is now a cultural/heritage center. A bench mark can be seen at the entrance gates as the following photo shows:



 The spot height is 26.1 ft.





Spot height on 6inch map 26.1 feet. 






Some bench marks are difficult see because of stone erosion and the growth of lichens on stone. One example of this is to be found on the North wall of St. John the Baptist church in Midleton. A bench mark (25.0 ft) has been cut into a stone approx. half way along the second course of blocks. Can you see it in the photo below?


In Fermoy a bench mark can be seen on the northern side of the town.The eastern wall around what was formerly Fermoy House carries a Brnch Mark with spot-height of 87.1 feet.






Waterford.
There are many existing bench marks areound Waterford City. The base of the Clock Tower on the city quays has one. 

The spot height is 18.8 feet.











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