417 



MAGNESIA. 



MAGNESIUM. 



411 



relating to the forests only. There were very extensive tracts of land 

 in England which were actually forests, uncultivated, and reserved for the 

 pleasure of the king ; and there were purlieus to these forests, all of 

 which were subject to a peculiar system of law, many parts of which 

 were felt to be oppressive, and from some of which this charter 

 exempted the people. 



The independence and rights of the church were also secured by the 

 great charter. 



Magna Charta has been printed in a great variety of forms ; there are 

 fac-similes of a copy of it which was made at the time, and still exists 

 in the British Museum, and of another preserved at Lincoln, and trans- 

 lations of it into the English language. It is thus so easily accessible, 

 that it will not be expected that we shall give a copy of it, or even a 

 complete abstract of its multifarious provisions, some of which are 

 completely obsolete, and the terms obscure. 



Such a concession from the king was not gained without a violent 

 struggle ; in fact he was compelled to yield it by an armed force, con- 

 sisting of a very large portion of the baronage, which he was far too feeble 

 to resist with effect. The names of the chiefs are preserved by the 

 chroniclers of the time, and in the charter itself ; and whenever recited, 

 they call up to this day a mingled feeling of respect and gratitude, the 

 respect and gratitude which men pay to those who have obtained for 

 them the extension of political privileges, though it may appear that 

 tnose privileges were nothing more than rights of which they had been 

 deprived, and to which therefore they may be said to have been justly 

 entitled. They appear the patriots of a rude age, and the mists of dis- 

 tance and antiquity obscure to us the selfishness and the other evils (if 

 such existed) which were manifested in the contest. The first name is 

 that of Robert Fitz- Walter, who belonged to the great family of Clare. 

 The title given to him as head of the host was Marshal of the Army of 

 God and of the Holy Church. Next to him come Eustace de Vesci, 

 Richard de Percy, Robert de Roos, Peter de Brus, Nicholas de Stute- 

 vile, Saier de Quenci, earl of Winchester, the earls of Clare, Essex, and 

 Norfolk, William de Mowbray, Robert de Vere, Fulk Fitz Warine, 

 William de Montacute, William de Beauchamp, and many others 

 of families long after famous in English history, the progenitors 

 of the ancient baronial houses of England. 



The charter was signed, or rather sealed, not in any house, but in 

 the open field, at a place called Runnymede, between Windsor and 

 Staines ; but it was not merely by an accidental meeting of two armies 

 at that place that this act was done there, for it appears by Matthew 

 of Westminster that Runnymede was a place where treaties concerning 

 the peace of the kingdom had been often made. All was done with 

 great solemnity. The memorable day was June 5, 1215. 



What was unwillingly granted, it could scarcely be expected would 

 be religiously observed. John himself would gladly have infringed or 

 broken it, as would his son King Henry III., but the barons were 

 watchful of their own privileges, those of the church, the cities, the 

 boroughs, and of the people at large ; and King Henry was led to make 

 one or more solemn ratifications of the charter. To keep the rights 

 thus guaranteed fully in the eyes of the people a copy was sent to every 

 cathedral church, and read publicly twice a year. 



See the work of Sir William Blackstone, entitled ' The Great Charter 

 and Charter of the Forest (on Public Wrongs), with other authentic 

 Instruments ; to which is prefixed an Introductory Discourse concern- 

 ing the History of the Charters.' Oxford, 1759, 4to. He wrote also 

 an express treatise on this charter. An exact fac-simile has been 

 engraved and published of the charter, from a copy preserved in the 

 archives of the cathedral church of Lincoln, with other of the greater 

 charters. In the first volume of ' The Statutes of the Realm,' pub- 

 lished by the Board of Commissioners on the Public Records, these 

 charters are all printed, with English translations of them. 



MAGNESIA. [MAGNESIUM] 



MAGNESIA, MEDICAL PROPERTIES OF. Oxide of mag- 

 nesium, termed also, from the mode of procuring it, calcined magnesia, 

 or magnesia usta, is an alkaline earth possessing the usual qualities of 

 alkalies in their habitudes with acids, and likewise the peculiar property 

 of exciting generally purgative action of the intestines. This last- 

 mentioned power gives it a distinctive character among alkaline 

 remedies, as it can be employed not merely to counteract acidity, but 

 also to remove the exciting cause when that consists in the presence of 

 crude or undigested acid-yielding materials in the stomach. Its action 

 as a purgative seems mainly to depend upon its meeting with acids in 

 the stomach, and so forming soluble salts. .When these are not present 

 the magnesia remains undissolved, and if used repeatedly may accumu- 

 late' in the intestines, and, becoming agglutinated by the mucous 

 secretions, give rise to much uneasiness. Hence some other aperient 

 should from time to time be given. [ANTACIDS.] When however 

 acidity exists, either along with constipation or diarrhoea, more 

 particularly in children, from the milk disagreeing, or from a diet 

 unsuited to their delicate organs of digestion being forced upon them, 

 magnesia is a very proper medicine, especially as it appears to possess 

 a specific power of diminishing gastrointestinal irritation. (Hufeland, 

 quoted in Pereira's ' Materia Medica.') It is generally expedient to add 

 rhubarb to it, and combine it with some carminative. In such a state 

 of combination it is peculiarly useful in what is termed diarrhoea 

 crapulosa, arising from too great a mixture or too large a quantity of 



XBTS ADD SCJ. CIV. VOL. V. 



Where it is determined to use magnesia, and sufficient acid does not 

 exist in the stomach to ensure the formation of a soluble salt, a little 

 lemon-juice may be added to it. The subcarbonate of magnesia has 

 nearly the same action as the calcined magnesia, but when it meets 

 with acids in the stomach effervescence takes place, accompanied with 

 a disengagement of carbonic acid gas, which in some cases is incon- 

 venient, in other instances extremely beneficial. In some almost 

 uncontrollable irritations of the stomach, where food and medicines are 

 alike rejected, subcarbonate of magnesia will be retained, and, by 

 allaying the irritability, allow other remedies to be subsequently 

 employed. Both the subcarbonate and the calcined magnesia are much 

 used to correct heartburn, and to check the lithic acid diathesis ; but 

 their employment requires much judgment and attention [ANTACIDS ; 

 ANTALKALIES], as persisting too long in the employment of this 

 or any alkaline preparation brings on a phosphatic condition. 



Sulphate of Magnesia, or Epsom salts, in the ordinary form, as met 

 with in the shops, are small acicular crystals. This renders them 

 liable to be confounded with those of oxalic acid ; to avoid which the 

 sulphate may be dissolved, and by recrystallisatiou they are obtained 

 in large four-sided prisms, or four-sided pyramids. The taste of 

 sulphate of magnesia is bitter and very unpleasant ; but this is very 

 much lessened by large dilution in water, which at the same time 

 increases the purgative action of the salt, or by adding magnesia, or by 

 giving it in compound infusion of roses and adding a few drops of 

 dilute sulphuric acid, which augments the refrigerating property of the 

 medicine. The addition of a little common salt to a solution of sul- 

 phate of magnesia increases its cathartic powers. 



No saline medicine is so extensively employed as the sulphate of 

 magnesia as a purgative ; it is more rarely used as a diuretic or 

 diaphoretic. Its action as a purgative is in general mild and certain, 

 causing a considerable evacuation of the serous secretions of the 

 intestines, and so producing a cooling or lowering effect. At the com- 

 mencement of most inflammatory complaints and of fevers its employ- 

 ment is most beneficial. Its utility is often much increased by adding 

 to the solution a very minute portion of tartarised antimony, so as to 

 form the emetico-cathartie solution, which is found very serviceable in 

 the fevers of India, and in those of the summer and autumn of European 

 countries. 



Small doses of sulphate of magnesia in bitter infusions are valuable 

 in the treatment of dyspepsia accompanied with constipation. Many 

 of the saline mineral waters resorted to for the cure of indigestion are 

 chiefly indebted to the sulphate of magnesia for their purgative 

 properties. 



Sulphate of magnesia is a convenient antidote in cases of poisoning 

 by the salts of lead or baryta. The saccharate of magnesia is an 

 eligible form of exhibiting magnesia to children. 



Magnesiau limestone is sometimes employed for building, and is a 

 very durable stone : it is however one of the most deleterious stones 

 for masons to hew, as the gritty particles very speedily occasion 

 disorders of the lungs, followed by early death. The mouth and 

 nostrils of the workman should therefore always be defended by 

 wearing a gauze mask. 



MAGNESIUM (Mg). This metal was first obtained by Sir Humphry 

 Davy, but its oxide or ma ,nesia, and carbonate, or magnesia alb", have 

 been known since the commencement of the last century. Its com- 

 pounds are frequently met with in the inorganic kingdom, but are not 

 so abundant as those of lime. 



Magnesium may be obtained from its chloride by heating with 

 potassium or sodium, or by subjecting the same salt to a voltaic 

 current obtained by means of a few cells of a Bunsen's battery. 

 Deville and Caron give the following details for the reduction of the 

 metal. Six parts of chloride of magnesium are well mixed with one 

 part of a fused and powdered mixture of chloride of potassium and 

 sodium, one part of pure fluoride of calcium, and one of sodium in 

 small pieces. The mixture is transferred to a red-hot earthen crucible, 

 fitted with a lid. After some time the reaction takes place, and when 

 the hissing noise has ceased, the lid of the crucible is removed, and the 

 mixture stirred with an iron rod until the whole appears uniformly 

 mixed, and the upper portion of the liquid mass is clear. The crucible 

 is then removed from the fire, and when the saline mass is nearly 

 solidifying, it is to be stirred with an iron rod so as to collect the 

 suspended particles of metal. When cold, the mass is broken up, and 

 the globules of crude magnesium picked out. 



The metal thus obtained may be purified by placing it in a carbon 

 tray, and heating it to whiteness in a carbon tube, a current of hydro- 

 gen being at the same time passed over it ; it is subsequently re- 

 melted with chloride of magnesium, chloride of sodium, and fluoride 

 of calcium. 



If, in the above process, the current of hydrogen is rapid, the 

 vapour of the magnesium is to a certain extent carried out of the tube, 

 and on being ignited, burns with an exceedingly beautiful flame. 



Magnesium is a metal of silvery white colour, and semi-crystalline 

 or fibrous fracture. It fuses and votalilises at about the same tempe- 

 rature as zinc, to which metal it in many other points bears a very 

 close analogy. It is malleable and ductile, may be easily polished, 

 readily filed, and yields well to the chisel. Its specific gravity is 1'75. 

 It doej not tarnish in dry air, and in a damp atmosphere oxidises but 

 slowly. This metal takes fire at about the temperature at which glass 



I K 



