A M M 



AMERICA, North. See United States. 



AMES, a townrtiip of Ohio, in the county of Athens, 

 having 608 inhabitants. 



AMESBURY, a town of the Maffachufetts, in EtTex 

 county, having 1890 inhabitants. 



AMHERST, 1. 3, r. 10,548 ; 1. 4, r. 5207. 



Amherst, 1. 6 from the bottom, r. 1554. Add — Alfo, 

 a town of Maffachufetts, in the county of Hampfhire, having 

 1469 inhabitants. 



AMI A, in Ichthyology, a genus of the abdominal fifhes, the 

 •charaders of which are, that the head is bony, naked, rough, 

 with confpicuous futures ; teeth, both in the jaws and palate, 

 c-Iofe-fet and ftiarp ; the two cirri near the noftrils ; the gill- 

 membrane twelve-rayed ; and body fcaly. There is one 



fpecies, iiiz. , , r 



Calva ; the Carolinian Amia, with a black fpot at the bale 

 of the tail. This is a fmall frefh-water filh, inhabiting feme 

 parts of Carolina. Defcnbcd by Linnaus, from a fpecimen 

 fent from Carolina by Dr. Garden. 



AMITY, in Geography, a townfhip of Pennfylvania, in the 

 county of Berks, containing 1 090 inhabitants. 



AMMODYTES, in Ichthyology. Add — The ammo- 

 dytes tobianus is the launce with the lower jaw longer than 

 the upper. It conceals itfelf about a foot in the fand, with 

 its body rolled into a fpiral form ; it is dug or drawn up, 

 and ufed by the fifhermen as a bait ; it is alfo confidered as 

 a delicate article of food. The general length is from eight 

 to ten inches. The launce lives on worms, water-infeds, and 

 fmall fithes, and even occafionally on thofe of its own fpecies. 

 It is itfelf preyed upon by the larger fifhes, and particularly 

 by the mackarel. It fpawns in the month of May, depo- 

 fiting its eggs in the mud near the edg^s of the coall. The 

 fwimming bladder is wanting, fo that the animal is fitted only 

 for a littoral refidence ; and its fcales are fo fmall that they 

 have been wholly overlooked, and their exiftence difputed 

 by fome ichthyologifts. Shaw. 



AMMONIA, in Chemtflry. The following additions to 

 our knowledge, refpeding the volatile alkali, have been made 

 5ince that fubjeft was treated in the Cyclopaedia. Water, as 

 has been already ftated, by abforbing ammoniacal gas in- 

 creales in bulk, and becomes fpecifically lighter. The tol- 

 lowing table by Mr. Dalton exhibits the quantity of am- 

 monia contained in ammoniacal folutions of different fpecific 

 gravities. 



A M M 



When potaflium or fodium is heated in ammoniacal gas, 

 the metal becomes changed to an ohve -green colour, and 

 lofes its metallic luftre ; at the fame time a portion of the 

 gas is abforbed, and a quantity of hydrogen emitted, cxaftly 

 equal to the quantity that would be evolved if the potaflium 

 or fodium were put into water. If the olive-green matter 

 be heated, it gives out three-fifths of the ammonia abforbed, 

 two-fifths in the (late of ammoniacal gas, and one-fifth in the 

 ftate of hydrogen gas and azote. Sir Humphrey Davy, 

 having heated the ohve-coloured matter ftrongly in a plati- 

 nium tube, obtained nearly the whole of the ammonia ab- 

 forbed, though about three-fifths of it were in the ftate of 

 azotic and hydrogen gas. If the olive-coloured matter be 

 placed in contaft with a very little water, it is converted into 

 potafh, or foda and ammoniacal gas, and the gas is juft equal 

 to what the metal had abforbed. If it be placed in contaft 

 with a metal and heated, an alloy of the metal with potaf- 

 fium or fodium is obtained. 



For thefe curious fafts we are indebted to Gay Luflac and 

 Thenard, and Davy. Dr. Thomfon thinks they (hew that 

 potaffium and fodium have the property of decompofing 

 ammonia, and combining with its azote, while the hydrogen of 

 the ammonia is fet at liberty ; and the azoturet formed, he 

 thinks, combines with a portion of the remaining undecom- 

 pofed ammonia. He acknowledges, however, that there are 

 fome objeftions to this opinion ; and the fafts accord better 

 with the opinion, that an unknown compound of azote and 

 hydrogen unite with the alkaline metal, while the com- 

 pound thus formed combines with a portion of undecom- 

 pofed ammonia. 



A curious experiment made by Berzelius and Pontin 

 induced Berzelius to draw the conclufion that ammonia is 

 compofed of an unknown metallic bafis, which he has called 

 ammonium, united to oxygen. This experiment has been 

 fince confirmed by fir H. Davy, Gay Luffac, and others, 

 and is as follows : 



When mercury is brought in contaft with ammonia at 

 the negative end of a galvanic battery, it gradually increafes 

 in vdlume, and is converted into a foft folid, having all the 

 appearances of an amalgam. The experiment fucceeds 

 better if fal ammoniac (lightly moiftened be fubftituted for 

 liquid ammonia. This amalgam, at the temperature of 70*' 

 or 80°, is a foft folid, of the confiftence of butter ; at 32° it 

 is a firm cryftallized mafs, having a fpecific gravity below 3. 

 When espofed to the air, it foon becomes covered with a 

 cruft of carbonate of ammonia. When thrown into water, 

 hydrogen is evolved equal to half its bulk, the mercury is 

 revived, and the water becomes a weak folution of ammonia. 

 When confined in a given portion of air, the air increafes in 

 bulk, and pure mercury appears. Ammoniacal gas, amount- 

 ing to li or l^ the volume of the amalgam, is evolved ; and a 

 quantity of oxygen equal to -^th or ^th of the ammonia dilap- 

 pears. When thrown into muriatic acid gas, it becomes coated 

 with muriate of ammonia, and a httle hydrogen is difengaged. 

 In fulphuric acid it becomes coated with fulphate of ammo- 

 nia and fulphur. All attempts to preferve this amalgam 

 failed, from the impoflTibility of obtaining it fi-ee from water. 

 When put into a glafs tube, or when confined under naphtha 

 or oils, the mercury feparated, ammonia was lorracd, and a 

 quantity of hydrogen evolved. 



Gay Luffac and Thenard confidered this amalgam as a 

 fimple compound of mercury and ammonia ; but no analogous 

 compound is known to chemifts, as mercury when it unites 

 to other fubftances, except metals, always lofes its metalhc 

 luftre. Thefe reafons induced Berzelius to form the above 

 opinion. Moft chemifts at prefent agree with Gay Luffac 

 and Thenard ; but if their opinion be well founded, we mutt 

 alter the notions entertained refpefting amalgams. 



The 



