lOi 



UXDULATORY FORCES. LIG 11T. 



[VEGETABLE OILS. 



purified, is very little iiiferior to iperm oil : it does not 

 clog the wick, or congeal in cold weather, and it burns 

 with a clear white flame, which U tolerably free frm 

 smell About 20,000 tons of whale oil and spermaceti 

 are annually unj..>i :ol into this country. 



(>-. ) Seal oil is procured from several species of ;>/io- 

 eula. The common teal (Phoca vitulina) is captured in 

 Urge numbers on the shores of Newfoundland : indeed, 

 we are informed that, during a good year, hundreds of 

 thousands are taken in that locality, for the sake of 

 the nil which they yield. They are also killed on the 

 n.'i th.Tii coast of Scotland, in the Orkneys. Shetland^, 

 and on the shores of Greenland. To the inhabitants of 

 tlio last-namod locality the seal is invaluable; fur it 

 furnishes tln-m witli food, raiment, and oil. The animal 

 is usually captured with spears or harpoons, and some- 

 times it is shot. As soon as it is dead, the skin i 

 stripped off, and then the fat is removed and boiled 

 :i in copper or iron vessels. Seal oil, like the pre- 

 ceding, is not much disposed to thicken ; and hence it 

 is well suited for combustion in lamps. 



(d.) Walrus oil is obtained from the morse or sea- 

 cow (Trifhecus ^Josmanta), many of which are annually 

 destroyed at Spitsbergen, and elsewhere, for the sake of 

 the skin, oil, and teeth. We do not receive the oil into 

 commerce in this country, and consequently have little 

 or no opportunity of testing its value ; but it appears 

 that its qualities are not inferior to those of the last- 

 montioued oiL 



(e.) Fish oils are extracted from the bodies and livers 

 of fifth. As examples of the former, we may mention 

 the oils obtained from the herring (Clupea harenyits), 

 pilchard (Clupea pilchardus), and sprat (Clupea sprattus) : 

 all of which are procured by submitting the fish to great 

 pressure at the time that they are undergoing the process 

 of salting. Of the latter may be mentioned the oils of 

 cod (Morrhua vulgarin), ling (Gadus molva), skate (Muia 

 bat is, <fx.), turbot (Lota vulgar is), torsk (Srosmius vul- 

 garis), &c. The oil is obtained by placing the livers in 

 a tub which has a perforated bottom covered with small 

 branches of trees. As the livers putrefy, the oil drips 

 out, and is caught in a vessel placed underneath. At 

 other times the oil is extracted by boiling the livers in 

 an iron pot, and then squeezing them in linen bags. 

 Cod-liver oil is not much used for purposes of illumina- 

 tion, as it is a valuable remedy for the cure of many 

 diseases ; but the oil of ling is extensively prepared by 

 the poor of the Orkneys and western islands of Scotland, 

 where it is employed as a common lamp-oil. All these 

 oils are somewhat of a drying nature, and therefore 

 become thick after a time ; besides which, unless great 

 care has been taken in their preparation, they are sure 

 to have a most unpleasant, fishy, or putrid odour. 



(/.) Lard oil, and the oleine from tallow and other 

 i-il fats, is obtained from the solid fats by slightly 

 ;u mini; thriii, and then submitting to pressure. This 

 oil is apt to deposit solid matter in cold weather, and 

 thus to become thick ; but the properties of the oil are 

 otherwise very good ; and, consequently, it is well suited 

 for combustion in lamps. The oleic acid, which is pro- 

 cured during the manufacture of stearic and inargaric 

 acids for candles, is not lit for illuminating purposes ; 

 for, although it gives out a very good light during its 

 combustion, yet it is so apt to clog the wick from the 

 impurities which it contains, that, in the course of a 

 very short time, the lamp ceases to bum. Were it not 

 for this, oleic acid might be extensively employed as an 

 illuminating agent. 



Vtgttable. OUt. (a.) Olive oii. This is furnished by 

 the fruit of OUa Europaa, of which there are two varieties 

 namely, the Umgifolia of France and Italy, and the 

 latifolia of Spain. The olives are gathered as soon as 

 tlmy are ripe, and this takes place early in November. 

 In France, where the beat oil is prepared, the fruit is 

 bruised in a mill directly it is gathered ; it is then 

 wrapped in a sort of matting, and submitted to pressure. 

 The oil which runs out is called virgin oil, and is kept 

 separate for table and dietetical purposes. The cake is 

 removed from the press, broken up by hand, moistened 



with boiling-water, and re-pressed ; in this manner a 

 second quality of oil is obtained, which, on standing, 

 separates from the water with which it is mixed. The 

 cake that is left from this operation is called griij><"n, 

 and, generally, it is get aside to dry, in order that it may 

 be used for fuel ; but sometimes it is submitted to frr- 

 mentation, then wetted with boiling-water, and pressed 

 a third time, by which means a third quality of oil, 

 called gonjon, is procured, which is used for lamps and 

 machinery. 



In Spain the olives are allowed to ferment for a period 

 of ten days or a fortnight before they are crushed and 

 pressed. In this way a larger supply of oil is obtained, 

 but the quality is very inferior to that prepaiv<! fnun 

 the fresh nut. One of the reasons why this delay takes 

 place, is, that there are not sufficient presses in the oil 

 districts to perform the necessary work ; and hence the 

 several growers are obliged to wait their turn, and k< <]> 

 their olives ready for the mills. But, within the last 

 few years, considerable improvement has been effected 

 in this respect by the introduction of hydraulic presses; 

 and now a large portion of the oil obtained from Spain 

 is equal, or nearly equal, in quality to that of France 

 and Italy. 



The machinery employed by the Neapolitan peasants 

 in the preparation of GaUipolI oil, is of the rudest kind. 

 The olives are allowed to ripen to the fullest extent on 

 the trees ; and, as they fall off, they are collected by 

 women and cluldren, and carried to the mill. The oU 

 which is expressed is put into sheep or goat-skin bags, 

 and conveyed on the backs of mules to Gallipoli, where 

 it is allowed to clarify by standing in cisterns which are 

 cut out of the rock on which the town is built. When 

 it has become sufficiently clear by the deposition of 

 mucilage, water, and other impurities, it is run off into 

 skins, and conveyed to"bil-basins which are situated near 

 to the sea-shore. From these it is put into casks, and 

 exported. 



According to Sieuve, olives furnish about thirty-two 

 per cent, of oil twenty-one of which come from the pulp 

 (or pericarp) of the fruit, four from the seed, and seven 

 from the woody matter. 



In whatever way the oil is obtained, it must be clarified 

 and freed from mucilage, <ka, before it is fit for use. 

 This is usually accomplished by allowing the oil to stand 

 in a warm place for a fortnight or three weeks, during 

 which time it deposits impurities, and becomes clear. 

 It may also be refined by heating it for a short time with 

 a weak solution of potash or soda, and then allowing it 

 to stand ; or it may be deprived of its acid congealable 

 matter, by exposing it for some time to the action of a 

 piece of lead the bottle containing the oil and the lead 

 being placed in a window, or other place where it will 

 receive the direct rays of the sun. In this way the oil 

 used by watchmakers and machinists is refined. The 

 best variety of olive oil is called Florence oil, which is the 

 produce of Aix, in France ; while the worst is the Spanish. 



In this country the price of olive oil renders it too 

 costly for lamps ; but in Italy, Spain, and France, it is 

 extensively employed for such purposes. It burns with a 

 clear white light, and does not emit any unpleasant 

 odour; besides which, it is not a drying oil, and is 

 therefore not likely to clog the wick. When it is idnl- 

 terated with poppy, nut, or sessama oils, its properties 

 are very much deteriorated. 



(6.) Almond oil is extracted from the kernels of the 

 common almond (amygdalua communis), of which, as in 

 tin 1 case of the olive, there are two varieties; namely, 

 the sweet (dulcis) and bitter (amara), both of which 

 yield the oil of commerce. The almonds are agitated in 

 bags, so as to separate a portion of their brown skin, 

 then crushed in a mill, and, after being folded in canvas 

 bags, they are subjected to pressure between cast iron 

 plates. That which runs over first is the best. The 

 residue is then heated and again pressed, by which 

 means an oil of inferior quality is procured. When tirst 

 obtained, the oil is thick and discoloured ; but by repose 

 in a warm place, or by filtration through paper or sand, 

 it becomes clear. Almonds yield from twenty-two to 



