important subject of the diurnal variation of the magnetic needle occupied
much of his attention, and on this he made a series of observations in 1794 and
the two following years, at Bencoolen, Sumatra, and St. Helena, which he com-
municated in 1798 to the Royal Society, who published them in their Transactions, and elected him a Fellow in 1800. About the last-mentioned period he
also returned to Britain, and was appointed lieutenant-colonel of the Royal
Clan- Alpine Regiment, and commandant of the Royal Edinburgh Artillery.
After his arrival, the life of Colonel Macdonald waa one of diligent useful authorship, so that his history from this period is best comprised in the titles of his works, and the dates of their publication. Of these we give the following list:—
In 1803 he published "Rules and Regulations for the Field Exercise and Manoeuvres of the French Infantry, issued August 1, 1791; translated from the French, with Explanatory Notes and Illustrative References to the British and Prussian systems of tactics," &c., &c., in two volumes 12mo.
In 1804, when he belonged to the 1st Battalion of Cinque Ports Volunteers, and when every kind of military instruction was most needed for our home-bred soldiery, while in training against the menaced invasion of the country from France, Colonel Macdonald published another work, in one volume, entitled, "The Experienced Officer; or, Instructions by the General of Division, Wimpffen, to his sons, and to all young men intended for the military profession, being a series of rules laid down by General Wimpffen, to enable officers of every rank to carry on war in all its branches and descriptions, from the least important enterprises and expeditions, to the decisive battles which involve the fate of empires. With Notes and an Introduction."
In 1807, while chief engineer at Fort Marlborough, he published "Instructions for the Conduct of Infantry on actual Service." This was also translated from the French, and published in two volumes, with explanatory notes.
In 1808 appeared his first work upon a subject which had employed his attention for years. This was "A Treatise on Telegraphic Communication, Naval, Military, and Political," 8yo, in which he proposed a different plan from that hitherto adopted.
In 1811, Colonel Macdonald produced a work in startling contrast to his former subjects, but which was only one among the studies of a comprehensive philosophic mind, under the title of " A Treatise, explanatory of the Principles constituting the Practice and Theory of the Violoncello." This work was published in one volume folio.
In 1812, reverting to his military avocations, he published a translation of "The Formations and Manoeuvres of Infantry, by the Chevalier Duteil," 12mo. This was the last of his productions in military science, and, as may be surmised from the date, the last that was needed for the French science of warfare was now well understood by our armies, as their hostile instructors were learning to their cost. This fact, however, shows the judiciousness of the plan which Macdonald had adopted as an expositor of warlike science, and indicates in some measure the probable benefit with which his own individual labours were followed.
In 1816, Colonel Macdonald returned to the important subject of telegraph communication, by publishing his "Telegraphic Dictionary," a laborious work, containing 150,000 words, phrases, and sentences. The estimate formed of the value of this work was shown by the directors of the East India Company, who
