The cover image on the issue of Scientific American from a century ago shows a large howitzer being loaded (shell and propellant were loaded separately) at the Battle of the Somme, which petered out on November 28, 1916. The article mentions the increasing value of large artillery pieces in static trench warfare:

“With the opening of the great Battle of the Somme at the beginning of July, the initiative on the Western front passed from the Germans to the French and British. During the progress of this battle (the greatest in the history of the world) the attack has steadily gained ground and the gains which have been made have almost invariably been held against the German counter-attacks. Undoubtedly, the principal agent in bringing about this change has been the enormous increase which has taken place in the heavy artillery of the Allies. This is made up of guns ranging in caliber from 4.7 inch up to 14-, 15- and 16-inch caliber. The greater part of this artillery is of the howitzer type, designed to rain a mass of vertically falling shells upon the trenches and machine-gun positions of the enemy. The howitzer which is shown in a fixed position, has a crane mounted at one corner of the base plate, which is used for lifting the shells from the ammunition car and depositing them on the shell-tray back of the breech of the gun. In the illustration this tray is thrown back out of position. The gun is guided in the horizontal position and when the tray is in service, it is swung forward into the horizontal position pivoting on the angle· iron yokes shown In the illustration. The four long cylinders, arranged in pairs, two above and two below the gun are the recoil cylinders, for checking the recoil of the gun and bringing it gradually to rest. The cylinders are filled with glycerine. The gun is returned to battery by means of coiled springs located within the cylinders.”

 
15-inch howitzer, emplaced during the Battle of the Somme, ready to fire, 1916. Credit: Scientific American, December 9, 1916

Another photo inside the issue shows the same gun ready to fire. The gun in question is almost certainly a 15-inch howitzer, emplaced in Englebelmer Wood on the Somme and serviced by the British Royal Garrison Artillery. The gun is one of only 12 of that caliber manufactured by the Coventry Ordnance Works. The 15-inch guns had a limited range, and were extremely heavy (94 tons) and difficult to move, but in the limited movement of trench warfare shifting the gun around was not too important and the large high-explosive shells fired—1,450 pounds—were considered to be useful. According to www.landships.info, 25,332 rounds were fired from these guns during the war.

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Our full archive of the war, called Scientific American Chronicles: World War I, has many articles from 1914–1918 on technological developments in the First World War. It is available for purchase at www.scientificamerican.com/products/world-war-i/