Multiple screws were used as early as our civil war on some vessels known as tin-clads on the Mississippi, their adoption being necessitated by the shallow draft. Twin screws were first used in war vessels where the necessity for keeping the machinery below the deck would not allow of all the power being conveniently used on a single shaft, but the great advantage they possess of security against total disablement and for maneuvering soon made them the rule for all naval vessels large enough to admit of them. They were much longer in coming in the merchant service where the limitations on naval machinery do not obtain, but since the era of the very large transatlantic steamers beginning with the Paris and New York," and the Teutonic and Majestic," all very large vessels have been built with twin screws. In the early steamers, almost the only independent steam auxiliary was a single pump which could be used for feeding the boilers while under banked fires or with the engine stopped, and for pumping the bilge. The other pumps were attached to the main engine. Such things as steam capstans and winches, steam steering gear, distilling apparatus, evaporators, forced draft blowers, and electric light engines, were not dreamed of. As time went on and the size of vessels increased, steam capstans and winches and steam steering engines came in. Then it began to be found desirable, particularly for naval engines, to remove all the pumps from the main engine, leaving it nothing to do but turn the propeller, and this brought, about independent air and circulating pumps and feed pumps. Further progress introduced the distiller and evaporator, the forced-draft blowers, and the electric light engine. Submarine boats made a brilliant performance at the recent maneuvers which the French navy carried out in the bay of Toulon. This is the first time that such maneuvers have been held in France. The idea was to combine the operations of the submarines of the port with the torpedo boats which form part of the defending fleet. The operation was as follows: A polygon had been traced in the great harbor. This polygon, which had a surface of some 3,000 square yards, was formed on one side by the shore and on the others by imaginary lines which had been determined in advance. A squadron composed of six torpedo boats of the fleet, headed by the destroyer La Dragonne," was detailed to defend and keep a lookout upon the polygon. On the other hand, five submarines were to traverse the space from one end to the other, without being seen or localized by the torpedo boats. The maneuver took place during the forenoon. It proved to be of a most instructive character, and gave some very conclusive results as to the operation of the submarines. The torpedo boats, which had an entire freedom of movement, ranged themselves at the extremity of the polygon, and facing the shore, on a line parallel to the latter, so as to have a wide field of vision before them. The sea was remarkably calm and exceptionally transparent at that time, which gave the least favorable conditions for the submarines. Besides, these small craft are the oldest of the series and the first to be built, so that they had not the benefit of the great improvements which have been recently made. The ,;Zd," the Gymnote," and three other submarines of the same type were ranged in line. In spite of the clearness of the water, the freedom of movement of the torpedo boats, and the sharp lookout which the officers and crew kept up in order to note the smallest disturbance at the surface, the five submarines were able to traverse the whole width of the polygon and were quite invisible, and no one was able to reveal their presence or to say at what time they had passed across the space. Only one ot the torpedo boats, the No. 140, in the report which it presented to the commandant of the defense, stated that during a few seconds a slight bubbling was noted, this no doubt being caused at the surface of the sea by a periscope which came near the top, but the duration of the disturbance was so short that no exercise of sighting could be made, and in spite of the efforts which were made at once, it was quite impossible to discover the path of any of the submarines. The naval authorities here consider that this experiment which is tried for the first time with the torpedo boats and submarines, is among the most important and conclusive, and justifies the confidence which the navy has in the good performance of the submarines. The railway companies in Switzerland have determined that for the future all children under 2 feet .1 inch in height will be passed at half fare, and those above, whatever their ages may be, will be treated exactly as adults. At each station, near the booking-office, a measuring machine is to be fixed, and whenever a child applies for a half-fare ticket it will be invited to stand under the scale.
This article was originally published with the title "Engineering Notes" in SA Supplements 60, 1539supp, 5 (July 1905)