SAFETY-LAMP 



SAFFLOWER 



71 



experimented with, they say : ' Many of the more 

 secure lamps are, however, rendered unsuitable for 

 ri.-giilar use by one or more of the following circum- 

 stances ; either they yield a very poor light, or 

 they require most careful handling to prevent the 

 light from being extinguished, or they are exceed- 

 ingly sensitive to oblique currents, or they are so 

 complicated as to present great difficulties in 

 putting them together and lighting them.' The 

 Commissioners add : ' But there are four lamps in 

 which the quality of safety, in a pre-eminent 

 degree, is combined with simplicity of construction 

 and with illuminating power at least fully equal 

 to that of any of the lamps hitherto in general use. 

 These are Gray's lamp, Marsaut's lamp, the lamp 

 of the latest pattern proposed by Evan Thomas 

 (No. 7), and the bonneted Mueseler lamp. With 

 the last care must be taken to avoid a considerable 

 inclination to the vertical direction." 



Of these four lamps the one by M. Marsant, of 

 the Besseges Collieries, Gard, France, seems to 

 have become the favourite ; at least it is now very 

 largely used. Like some other forms it is in prin- 

 ciple a bonneted (Manny, but it is made with 

 either two or three wire- 

 gauze covers, e, e, c, fig. 2. 

 In common with the other 

 three lamps mentioned 

 above as exceptionally safe, 

 the lower portion g consists 

 of a glass cylinder surround- 

 ing the light on the top of 

 which the gauzes are fixed. 

 The curved arrows show 

 how the air enters to sup- 

 port combustion, and the 

 straight arrows how the pro- 

 ducts of combustion escape 

 at the top ; w is the wire 

 for trimming the wick. 

 This lamp made with three 

 gauzes will not cause an 

 explosion in so strong a cur- 

 rent as 50 feet per second, 

 or even when the inner 

 gauze is at a bright red 

 heat, unless it is kept in the 

 fire-damp till the glass 

 cracks ; it may be said to 

 be safe for three or four 

 minutes. With two gauzes 

 the light is two-thirds and 

 with three gauzes it is one- 

 half that of a standard 

 candle, the light of the two- 

 gauze kiln! )>eing three and a half times greater 

 than that of a Davy lamp. 



To prevent safety-lamps being surreptitiously 

 opem-d in a mine it is necessary that they should 

 be locked. One of the best ways of doing this is 

 to fasten the oil-vessel to the other part of the 

 lamp by a riveted lead-plug, and impress it at 

 each end with a mark which should be varied from 

 day to day. Lamps have also been constructed 

 wliirh go out when opened, and one kind can 

 be opened only by help of a powerful magnet. 



As respects the illuminanta for a safety-lamp 

 seal-oil and refined rape-oil are the two staples, 

 but the former is superior to the latter in burning 

 qualities. Both are improved in this respect by 

 tne admixture of two parts of either with one part 

 of petroleum or paraffin-oil of a flashing-point not 

 lower than 80 F. This is considered a safe mix- 

 ture. A patent was granted on February 16, 1889 

 (No. 2779) to J. Thorne for what is called the 

 Tlioniehnrry miners' safety-lamp. The peculiarity 

 of tliis lamp is that it is adapted to burn a heavy 

 petroleum oil with a high flashing-point, and gives 



Marsant Lamp. 



a light from one to one and a half caudle-power, 

 which is much greater than that of other modern 

 safety-lamps. It has been tested by Sir F. Abel 

 and Professor Dewar, who report that the lamp 

 fulfils the conditions essential to safety as laid 

 down by the recent Commission on Accidents in 

 Mines. 



Electric glow-lamps are used for lighting up pit- 

 bottoms and roadways, though hardly as yet for 

 illuminating the working faces of mines. But port- 

 able, self-contained electric lamps that are perfectly 

 safe have l>een devised which will furnish for several 

 hours a considerably better light than that of the 

 best safety-lamp in use. As air is completely 

 excluded from these lamps they give no indication 

 of the condition of the atmosphere of a mine, so 

 that their employment would require the use of 

 fire-damp detectors, and also of some ordinary 

 safety-lamps. 



Safety-valve, an apparatus the duty of which 

 is to allow the steam to escape from a boiler when 

 it reaches a certain pressure, and thus to prevent 

 undue strain on the boiler-plates. The figure shows 

 in outline the principle of this valve : a, a is a dome 

 on the top of the boiler-shell ; b is a conical brass 

 valve resting on a seat, which has been smoothly 

 bored for its reception ; e is the fulcrum of a long 

 lever e, f, from which at d there is a projection 

 resting on the top of the valve. The end, /, of the 

 lever is held down against the steam-pressure by 

 the spring h. The pull exerted by this spring can 

 be adjusted by a nut at /, and it is fitted with a 

 brass case, and an index so arranged as always 

 to point to a figure which indicates at what pressure 

 per square inch the steam in the boiler will l>e able 

 to lift the valve. For most stationary boilers a 

 weight which can be moved along the lever to any 

 desired posi- 

 tion is used 

 instead of the 

 spring. In 

 marine boilers 

 the lever is 

 frequently dis- 

 |>ensed witli 

 altogether, 

 and weights 

 act directly on 

 the valve. It 

 is also usual, 



and in steamers compulsory by law, to put two 

 safety-valves on each boiler, one adjustable at will 

 by the engineer, and the other (called the 'govern- 

 ment valve') enclosed in a case to which access 

 can only l>e obtained by means of a key in the pos- 

 session of the captain. The danger of explosion 

 through overloading the valves is thus obviated. 

 See also STEAM-ENGINE. 



Sllffi. or ASFI, a seaport of Morocco, stands on 

 a little bay on the Mediterranean coast, 120 miles 

 WNW. of the city of Morocco. It is a compactly 

 built place, dominated by a fine rained castle of 

 the sultans of Morocco dating from the 16th 

 century. The place was held by the Portuguese 

 for several years ; they abandonee! it in 1648. The 

 fortifications they built still stand in part. The 

 shrine of the Seven Sleepers here is visited by both 

 Moslems and Jews. Saffi was at one time the 

 chief seat of the trade of Morocco with Europe, 

 and, though it has declined since the rise of Moga- 

 dor, it still exports beans, maize, pease, wool, olive- 

 oil, &c. to the annual value of 151,600 (84 per 

 cent, to Great Britain), and imports cottons, 

 sugar, &c. to the average annual value of 66,900, 

 more than one-half from Great Britain. Pop. 9000. 



Safflower (Carthamus tinctorius), an annual 

 herbaceous plant with large orange-red flowerheads. 



