One of two profile gauges with concave profile which was used by the 3rd Earl of Rosse to measure the 72 inch mirrors used on the largest Rosse telescope. Profile gauge with concave profile 1844-1845
Two profile gauges, concave and convex which were used by the 3rd Earl of Rosse to measure the 72 inch mirrors used on the largest Rosse telescope. Two profile gauges 1844-1845
One of two profile gauges with convex profile which was used by the 3rd Earl of Rosse to measure the 72 inch mirrors used on the largest Rosse telescope. Profile gauge with convex profile 1844-1845