User:Gibmetal77/sandbox/Healy's Mortar
| Healy's Mortar | |
|---|---|
 Healy's Mortar cut into the solid limestone of the Rock of Gibraltar. | |
| Type | Mortar |
| Place of origin | Gibraltar |
| Service history | |
| Used by | British Army |
| Wars | Great Siege of Gibraltar |
| Production history | |
| Designer | Healy |
| Designed | 1771 |
| Manufacturer | Healy |
| Produced | 1771 |
| No. built | 1 |
| Specifications | |
| Length | 4 ft (1.2 m) |
| Diameter | 3 ft (0.91 m) |
| Maximum firing range | 500 yards (460 m) |
Healy's Mortar (sometimes spelled Healey's Mortar) is a mortar cut out of solid limestone in the western face of the Rock of Gibraltar in the British Overseas Territory of Gibraltar.
Construction
[edit]Healy's Mortar is located just north of the Apes' Den at Prince Ferdinand's Battery along Queen's Road in the Upper Rock area of the Gibraltar Nature Reserve.[2]
The cutting of a mortar out of solid rock was not Mr. Healy's original invention as a variant was already in existence below a fountain in what later became the Alameda Botanic Gardens. It was considerably older than Healy's and according to historian George Palao likely to be of the period towards the end of the second Moorish occupation or the beginning of the Spanish re-occupation which would coincide with gunpowder's first appearance in Europe.[2]
Healy however, chose to cut his mortar into the solid limestone of the Rock in a parabolic conoid at an elevation of 650 feet (200 m) above sea level. He achieved this by first cutting a plane surface at an angle of 45 degrees and boring a centre axis to the depth of 4 feet (1.2 m) perpendicular to the surface. He then used this centre hole to inscribe a circle 3 feet (0.91 m) in diameter onto the plane. The limestone's hardness meant Healy was unable to excavate the mortar's cavity by chipping away at the rock, so he instead bore further holes around the entire circumference of the circle, each inclined to the centre so they all ran to the base of the centre hole. The partitions between the holes were then cut away to loosen a cone of solid rock. This cone was later taken to England by Captain Bentinck aboard HMS Centaur (1759). Healy completed the construction of the mortar by chipping away at the rough rock cavity to shape it into a true parabola and finally polishing it smooth.[2] The idea of using this shape was that any load or charge would follow a parallel trajectory to its centre axis much in the same way as we now understand radio waves to travel from a modern parabolic antenna.[2]
Testing
[edit]At eight o'clock in the morning of 14 May 1771 the then Governor of Gibraltar, Edward Cornwallis, ordered for testing to begin on the stone mortar. The Southport Gates were closed and the drawbridge pulled up in anticipation of the experiments while the three guards between there and the South Barracks retired out of harm's way. The Governor had put a Colonel Philips in charge of the experiments and though Healy requested that the first shot be made with a charge of 50 pounds (23 kg) of gunpowder, the Colonel would only agree to 27 pounds (12 kg). Stones were collected for the first shot and a detachment of artillery assisted with loading the mortar.[2]
The powder was first placed in the mortar's base followed by a wooden tampion carefully placed to cover the charge. A quick match would then be conveyed via a copper tube through the tampion's centre to ignite the powder.
References
[edit]
- ^ Hughes, Quentin; Migos, Athanassios (1995). Strong as the Rock of Gibraltar. Exchange Publications. p. 263.
- ^ a b c d e Palao, George (1975). The Guns and Towers of Gibraltar. Ashford, Buchan & Enright. ISBN 0948466014.