113 



AERATED WATERS. 



114 



ball, with a email orifice in which a tube might be screwed. It served 

 to boil water in, for the purpose of creating steam. This instrument is 

 mentioned by Des Cartes, in his treatise on ' Meteors,' chap, iv., as used 

 in his time. It is now entirely out of use, unless we choose to consider 

 the boiler of a steam-engine as an telopile. This is by no means the 

 first instance in which a philosophical toy has been made of use to 

 the arts. 



.iRA, a point of time from which sube<ieitt years are counted, and 

 in some instances preceding years, as in the Christian sera. The origin 

 of the word cera is very doubtful. 



All nations who have any history to record have fixed their tpra at 

 some remote period, in order to embrace in their annals as large an 

 extent of time as practicable. The creation of the world would most 

 naturally present itself to those who might have any means of ascer- 

 taining the time of its occurrence, and the Bible would be the source 

 from whence the information might be obtained. But, unfortunately 

 for chronology, the Bible is not sufficiently explicit on the subject ; 

 and, although the Jews and some Christian nations do date from the 

 Creation, their computations of the period at which this event took 

 place differ to the extent of nearly 2000 years. Those whom this 

 uncertainty hag deterred, or who have had no knowledge of the 

 Scriptures, have contented themselves with more recent periods. The 

 ancient Romans adopted the epoch of their h'rst supposed political 

 existence, and the Greeks that of the first celebration or revival of the 

 Olympic Games, which were with them an important national festival. 

 Many nations have assumed some event closely connected with their 

 religious faith : thus, the early Christians of the East dated from the 

 persecution under the Emperor Diocletian, and those of Europe and 

 America, at the present day, from the birth of Christ. All the 

 followers of Mohammed have adopted, as an acra, the retreat of their 

 prophet from Mecca to Medina, which they call the Hegira. 



Many of these seras are arbitrarily and incorrectly fixed, and even 

 our own is erroneous by four years. But an error at the com- 

 mencement will not invalidate the dates of events recorded sub- 

 sequently, as any sera once assumed will be sufficient to show the 

 uucceBsioii of time, however incorrectly assigned to the period whose 

 name it bears. 



With one or two exceptions, all nations have reckoned time in 

 accordance with the course of the seasons ; they have always begun 

 their year at the same season, sometimes perhaps a little earlier, and 

 sometimes later, but invariably keeping near the original commence- 



llU'llt. 



H.M.. follows a list of the seras which have been or are most in use 

 among the civilised nations of the world, with the year of the Christian 

 teni in which they began : 



1. The year of the world according to the reckoning of 

 c.,ii.t. en tin i, |,|r, which was used in Russia until the 

 liegiiming of the 18th century, and is still employed 



by the Greek Church B.C. 5509 



~1. The year of the world as reckoned at Antioch, now 



used in the Abyssinian Church .... B.C. 5492 



[The Church of Alexandria originally assumed the year B.C. 5502 as 



the year of the Creation, but in the year A.D. 285 they discarded ten 



and thus acceded to the computation of Antioch.] 

 The year of the world used by the Jews . . . B.C. 3761 

 4. The Caliyuga, employed by the learned throughout 

 India, may be called an sera of the Creation, being 

 considered by the Hindoos as the commencement of 

 ilir present state of the world, or 'Iron Age' . . B.C. 3102 

 .">. The Olympiad*; the sera of the victory of Corccbus at 

 the Olympic games, used chiefly by the Greek histo- 

 rians after the age of Alexander .... B.C. 77f> 

 I N.I!. An Olympiad is a period of four years.] 

 ti. The Building of Rome : this is generally called the 



Viirninian ;cra B.C. 753 



1. Tin: Catonian sera of the building of Rome is* . . B.C. 752 

 . I he aera of Vicramaditya, in common use throughout 



India B.C. 56 



y. Tlie .Spanish sera, from the Conquest of S|in by 



Augustus, was employed in Spain, Portugal, Africa, 



and tin' Smith of France. In ome provinces this 



H.-ra was in use until the middle of the 15th century . B.C. 38 



1". The ;era of Saliva liana, in common use through the 



wmthern and western states of India . . . A.D. 78 

 1 1 . The sera of Martyrs, or of Diocletian, so called from 

 the persecution of the Christians in the reign of that 

 was much used by the early Christians, and 



i rttill employed in the churches of the East . . A.l>. 284 

 I-. Tli. H-WM, "ed by all Mohammedans, dates from the 



flight of Mohammed to Medina . . . . A.D. 622 

 1 3- ' ra dates from the birth of Christ ; the 



lie was (erroneously) supposed to lie 

 l>rn in i-allc-d l B.C., the following year 1 A.I). Many 

 authors call the year of our Lord's birth 0, and con- 

 sequently make the dates of all preceding events one 

 year less than by the common practice. 



See Idelcr'i ' Chronology,' p. 33-t. 

 i AMD SCI. D1V. VOL. I, 



The following rules will serve to show the year of the Christian sera 

 corresponding with that of any given rcra : 



1. When the commencement of the given sera precedes the birth of 

 Christ, subtract from the given year the number affixed to the sera in 

 the above list, and the remainder will be the year of Christ in which 

 the given year began. 



If the given year be less than the affixed number, subtract it from 

 that number, adding one ; the result will be the date before Christ. 



Examples. Required the Christian date answering to the year of 

 Rome 1754. 



From 1754 

 Deduct 75S 



The year 1001 A.D. corresponds with the year 1751 A.U.C. 

 Required the year B.C. answering to 707 A.u.c. 



From 753 

 lieduct 707 



40 

 Add 1 



The year 47 U.K. coincides -with 707 A.V.C. 



The reason is this : A.u.c. 707 means that an event took place in 

 that year : and therefore 753 706 or 47 years B.C. remain, and as all 

 the years B.C. before B.C. 47 have expired, the event must take place if. 

 the year B.C. 47. 



Required the year of Christ in which the year of the Jews 5613 

 began. 



From 5613 

 Deduct 3761 



Answer A.D. 1852 



2. When the commencement of the given tera follows the birth of 

 Christ, add to the given year the number affixed to the sera in the lint, 

 less one. The sum will be the year of Christ iu which the given year 

 began. 



Example. Required the Christian year in which 1031 of Martyr* 

 began. 



To the Riven year 1031 



Add the number in the list | , 



lessonej 283 



The year A.D. 1314 answers to the year 1031. 



All the above dates may be reduced to the Christian sera by the 

 same formula, except that of the Hegira, as the Mohammedans 

 allow only 354 days to the year. Mohammedan reckoning is thus at 

 variance with the course of the seasons ; their year now (1859) begins 

 hi July, and gains at the rate of a little more than three years in a 

 century. It will, therefore, be necessary to prepare any given date 

 from the Hegira by subtracting three years for every hundred, before 

 reducing it to the Christian sera. 



Required the year of the Hegira 1268. 



From 1268 



Subtract 3 years for every 1 3g 

 hundred ( 



Add the number in the list 

 less one 



1230 

 G21 



1851 



The year of the Hegira 12G8 began in the year 1851 A.D. 



8. The computation by Olympiads may be thus explained : for 

 instance, 01. Ix. 3 means that an event took place in the third year of 

 the aictieth Olympiad, and consequently in the year that followed the 

 expiration of 59 Olympiads (or 59 periods of 4 years each), and 2 more 

 years belonging to the 60th Olympiad ; or after the expiration of 238 

 years, and therefore / the year B.C. 538. 



AERATED WATERS. The term mineral waters has generally 

 been applied to those drinks in which water is combined, naturally or 

 artificially, with mineral ingredients having medicinal qualities ; but 

 when the water is simply impregnated with gases, the term aerated 

 waters becomes preferable. 



Bakewell's apparatus is one among many contrivances for producing 

 such liquids, for effervescing, aperient, tonic, and other purposes. Let 

 us select the manufacture of soda-water, as one example : The appa- 

 ratus employed consists of an upright vessel supported on a stand, and 

 furnished with pipes and valves. In the lower part of the apparatus is 

 a vessel called the generator, divided into two compartment* by n 

 horizontal partition. Sulphuric acid is placed in the .uppermost of 

 these compartments, and carbonate of soda in the lower. While the 

 vessel is at rest, the two substances are kept wholly separate ; but 

 when a working motion is given to it by making it oscillate on two 

 pivots whereby it is suspended, the acid drops at regular intervals 

 through a hole in the side of the upper compartment, and falls into 

 the lower one, where it mixes with the carbonate. A chemical inter- 

 change immediately takes place ; the soda leaves the carbonic acid and 



