March 15, 1889.] 



SCIENCE 



191 



America in 1839, we have to thanl< the English Admiralty. In 

 1837 he built a tug, having two propellers of 5^ feet diameter, m- 

 vited the British Admiralty to inspect it, and towed their barge at 

 a rapid rate ; but their lordships solemnly concluded, that, as the 

 motive power was in the stern, the novel craft would not steer. 

 Thus it was in America, in 1841, that he began to build the 

 " Princeton," the first naval vessel that ever carried her machinery 

 under the water-line, out of the reach of hostile shot. 



In 1839 Congress had authorized the construction of three war- 

 ships. In 1840 the secretary of the navy, in obedience to that law, 

 ordered two to be constructed. The question of whether steam 

 could or could not be successfully applied to war-vessels had not 

 then been solved, the fear of danger from ignition by fire prevailing 

 in the minds of all naval men. One of the officers of our navy, 

 Capt. William Hunter, submitted a plan by which wheels were to 

 be inserted in the bilge of the vessel on each side, — submerged 

 wheels. Ericsson had demonstrated his plan to be feasible, in his 

 experiments in England. The secretary of the navy, in authorizing 

 the construction of these two vessels, directed that one was to 

 be built on Ericsson's plan, and one on Hunter's plan. Hunter's 

 plan proved a total failure: Ericsson's plan laid the foundation of 

 the present steam marine. The " Princeton " was the first war- 

 propeller ever built on the face of the earth, and in her he brought 

 forward not only his propeller, but a great many appliances ap- 

 purtenant to steam navigation which have since been used in our 

 service. 



The honor of having built the first practical screw-steamer was 

 thus Ericsson's, — an invention which was matched by that of the 

 " Monitor," fifteen or twenty years later. 



Such a device was offered by Ericsson in 1854 to Napoleon III. 

 The story of what happened in 1862 is too well known to need 

 repetition here. By extraordinary energy and executive skill, the 

 " Monitor " was launched, with steam-machinery complete, a hun- 

 dred days from the laying of the keel plate, and arrived in Hamp- 

 ton Roads just in time to defeat, March 9, 1862, the Confederate 

 ironclad " Merrimac," which had destroyed the " Cumberland " 

 and " Congress," and was about to sink or disperse the rest of the 

 government's wooden fleet. Naval warfare was revolutionized. 



The Mechanics' Institute of New York offered its great gold 

 medal in January, 1840, as a prize for the best plan of a steam fire- 

 engine. Ericsson, having several years previously designed such 

 machines in England, among which may be mentioned the steam 

 fire-engine employed during the memorable fire at the Argyle 

 Rooms in London in 1830 (the first time fire had ever been extin- 

 guished by the mechanical power called forth by fire), had no dif- 

 ficulty in producing plans complying with the conditions of the 

 Mechanics' Institute in a manner warranting the award of the prize 

 offered. 



His caloric engine was produced in 1833. In 1853, a voyage of 

 the caloric ship " Ericsson," a vessel of 2,000 tons, 260 feet long, 

 from New York to Washington and back, showed, that, though 

 economical in fuel, the new heated-air motor could not produce 

 speed enough at sea for commercial purposes, nor compete on 

 any large scale with steam. Still, it has been applied successfully 

 in thousands of engines to minor useful purposes. 



Favored by the possession of a robust constitution and ample 

 means, Ericsson devoted many of his last years exclusively to the 

 investigation of solar heat, and to the determination of the mechan- 

 ical energy which the sun has in store for mankind when the coal- 

 fields become exhausted. A sun-motor (illustrated in Nature, 

 xxix. p. 217) erected in 1883 was found to develop under ordinary 

 sunshine a steady and reliable power. Although he was eighty-six 

 years old, and by no means well since the beginning of the year, 

 Capt. Ericsson continued to labor at this motor until within two 

 weeks of his death ; and, as he saw his end approaching, he ex- 

 pressed regret only because he could not live to give this invention 

 to the world in completed form. It occupied his thoughts up to 

 his last hour. While he could hardly speak above a whisper, he 

 drew his chief engineer's face close to his own, gave him final in- 

 structions for continuing the work on the machine, and exacted a 

 promise that the work should go on. 



No visitor was allowed to enter his workshop. Even his most 

 intimate friends have never gained entrance there. Nor has any 

 servant been in the room where the captain spent more than twelve 

 hours daily for thirty years. 



Here in his workshop, as it were, Ericsson lived, and here he 

 died, a recognized leader among those who have added to human 

 welfare, and honoring by his name the rolls of more than a score 

 of associations of learned men. 



THE DENIO FIRE-ALARM. 



We illustrate herewith a simple automatic fire-alarm combined 

 with an ordinary electric push-button, which is being manufactured 

 by the Denio Fire Alarm Company of Rochester, N.Y. The con- 

 struction and operation of the device will be readily understood 

 from the following description. In a thimble with an internal 

 flange at one end, an external hollowed flange at the other, is placed 



a spring slightly longer than the thimble. This spring, one end of 

 which bears against the internal flange, is compressed, and held in 

 place by a pin which passes through it, the head of the pin fitting 

 snugly in the recess made in the external flange of the thimble. 

 The pin is sufficiently long to project entirely through the orifice in 

 the internal flange end of the thimble. When the parts have been 

 put together, the pin is secured in place by soldering to the flange, 

 the solder used for this purpose being an alloy which will fuse at a 

 low temperature, 150'^ to 160° F. 



By removing the porcelain knob from any of the ordinary push- 

 buttons now in use, and substituting this thimble, the button is 



