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THE ADDEESS OF THE CHAIRMAN OF THE 

 PHYSICAL SECTION OF THE EOYAL SOCIETY 

 (E. SwABEECK Hall), AT THE OPENING MEETING 

 OF THE SESSION, 1865. Tuesday, Apeil 4th. 



No special subject has been selected for the opening address of this 

 session of the " Physical Section of the Royal Society of Tasmania." 

 But I think our time will not be mis-spent if I briefly direct your 

 attention to some recent discoveries, which have an important bearing 

 on philosophic research, and the .economic application of scientific 

 data to the comfort and welfare of the human rate. Out of many 

 such discoveries I choose three to pass a few comments upon. It has 

 been found that the illuminating and heat-giving rays of the sun 

 can be completely dissevered by passing the solar ray through a 

 solution of iodine or sulphide of carbon. The illuminating rays are 

 thus intercepted, while the calorific rays pass through the media with 

 such undiminished power that when concentrated to a focus gun- 

 powder can be ignited. The magnesium wire lighted, and even 

 platinum melted. To Professor Tyndall, of the Royal Institute 

 of London, science is indebted for the knowledge of this important 

 fact. For optical and other curious enquiries into the laws of heat 

 and light this discovery will be doubtless of much value, but I do not 

 see that it is likely to be of much practical worth in the daily business 

 of life. 



The second of my subjects, however, is one of immense practical 

 value, and is likely to supersede all our modern means of procuring 

 artificial light. By applying the great decomposing power of the 

 galvanic battery, the metal magnesium has been discovered. It much 

 resembles aluminium in its external qualities, though of much less 

 specific gravity. It can be drawn into a fine wire, like silver, and this 

 wire can be ignited and burnt in ordinary atmospheric air, and the 

 light eliminated is so intense that at sea it can be seen at a distance of 

 28 miles. At the same time the light is so pure that the photographer 

 is now independent of the sun light, and can procure pictures by its 

 use, of the inside of caverns, and other places where the sun light 

 cannot be made available. Mr. Knight, the pyrotechnist, a gentleman 

 not likely to be easily alarmed by a blaze,informs me that having had 

 a couple of inches of the magnesium wire given to him, he ignited 

 it, ar.d the intensity of the light, that suddenly burst forth, frightened 

 him, and that he at once commenced to puff it out, fearftil lest some 

 terrible explosion was about to occur. It is, however, one of the 

 many great advantages that will result from this interesting discovery, 

 that danger of all kind will be much diminished by its use for 

 domestic and public lighting. It emits no sparks, it gives forth by 

 its combustion none of the gases so deleterious to health, that are 

 generated in the combustion of all the hydro-carbons— as gas, wax, 

 oil, tallow, kerosene, kc, &c. It of course consumes the oxygen of 

 the air in a room, and Hberates the nitrogen, but the result is merely 

 a white powder,that may be collected for use, and stored m the domestic 

 medicine chest — oxide of magnesium, otherwise magnesia. The last 

 number of the Builder states that a Mr. Grant, in London, is con- 

 structing lamps in which to burn the wire, and render it of ready 



