Pasley endeavoured to improve the practice of military engineering. He visited a Lancasterian school in August of that year, and commenced a course of instruction for his non-commissioned officers. He composed an elaborate treatise on a similar principle to the systems of Bell and Lancaster, to enable the non-commissioned officers to teach themselves and their men without the assistance of mathematical masters, and to go through their course of geometry in the same manner as their company drills or their small-arms exercises. The system was found so successful at Plymouth that in March 1812 it was laid before a committee of royal engineers, who reported favourably upon it to the inspector-general of fortifications, and it was afterwards introduced on an extended scale into the schools at Chatham. While Pasley was at Plymouth he was temporarily commanding royal engineer of the district, a position in which, although so junior an officer, he was allowed, owing to his merits, to continue for nearly two years. He received a special allowance for which there was no precedent.
Pasley's energy and success, backed by the representations of the Duke of Wellington from the Peninsula as to the defective condition of military engineering in the field, resulted in the formation of the establishment for field instruction at Chatham, and in Pasley's appointment to the office of director of that establishment by Lord Mulgrave in June 1812, with the rank of brevet-major, antedated to 5 Feb. of that year. Pasley was promoted brevet lieutenant-colonel on 27 May 1813, and became a regimental lieutenant-colonel on 20 Dec. 1814.
In 1814 there appeared the first volume of his work on ‘Military Instruction;’ the second followed, and the third and last in 1817. The first contained the course of practical geometry before referred to; the two latter, a complete treatise on elementary fortification, including the principles of the science and rules for construction, many of which apply to civil as well as to military works. In 1817, finding that his men had been ‘most grossly ill-treated by the army bread contractor,’ he was led to inquire into the system under which the army was supplied with provisions, and he printed and circulated in 1825, but abstained from publishing, a volume containing the results of his investigations into the system of general or commissariat contracts. He recommended that it should be abolished in favour of the system of regimental purchases. Pasley's suggestions were partly the means of introducing better arrangements. In 1818 he published a volume of ‘Standing Orders,’ containing a complete code of military rules for the duties of all ranks in the army.
During his tenure of office as head of the instructional establishment at Chatham he organised improved systems of telegraphing, sapping, mining, pontooning, and exploding gunpowder on land and in water, and laid down rules for such explosions founded on careful experiment. He also prepared pamphlets and courses of instruction on these and other subjects. A volume on ‘Practical Architecture’ was especially valuable. In his leisure time he learnt the Welsh and Irish languages from Welsh and Irish privates of the corps of sappers and miners. His work on the ‘Practical Operations of a Siege,’ of which the first part was published in 1829 and the second in 1832, is still an authority, and was the best text-book at the time that had been written in any language on that subject. Every operation of the siege was treated as a separate study, and it exposed various mistakes into which French and German authors had fallen. It was translated into French, and published in Paris in 1847.
Pasley was promoted brevet-colonel on 22 July 1830, and regimental colonel on 12 Nov. 1831. In that year he prepared a pamphlet, and in May 1834 he completed a volume of 320 pages, on the expediency and practicability of simplifying and improving the measures, weights, and money used in this country, without materially altering the present standards. By this work he hoped to bring about the result that, in the words of sect. 2 of the Act 27 George III, cap. x., there should be ‘only one weight, one measure, and one yard throughout all the land.’ He advocated the adoption of the decimal systems, and opposed the introduction of the French units into this country.
In May 1836 he commenced a work on ‘Limes, Calcareous Cements, Mortar, Stuccos and Concretes, and on Puzzolannas, Natural and Artificial Water Cements equal in efficiency to the best Natural Cements of England, improperly termed Roman Cements, and an Abstract of the Opinions of former Authors on the same Subject,’ 8vo. The first edition was published in September 1838. It contains several discoveries, the result of experiments at Chatham, and led at once to the manufacture in large quantities of artificial cements, such as Portland, patent lithic, and blue has. A second edition was published in August 1847.
In connection with experiments on the explosion of gunpowder under water, Pasley carried out the removal of the brig William and the schooner Glenmorgan from the
