POLTTECHNIC ASSOCIATION PROCEEDIIfaS, 397 



quantities of starch and gum. The powder is prepared by adding 

 a little ammonia to an acid solution of phosphate of lime, and 

 filtering with animal carbon, then evaporating until concentrated, 

 when five per cent of gelatinous silica is added; the whole is then 

 evaporated and the resulting crystals are pulverised 



ANIMAL JfECHANICS, 



The Rev. Samuel Houghton, of Trinity College, Dublin, already 

 favoi-ably known to the scientific world by his investigations relat- 

 ing to animal physiology, has lately furnished new proofs that the 

 force of a muscle is proportioned to the area of its cross section, 

 and that of the tendon which conveys its power to a distant point. 

 He estimates the contractile force of muscle generally at 109.4 

 pounds per square inch of cross section. 



POWDER *K)R CLEA>TNG JEWELRY. 



The high price of an excellent powder much used by European 

 jewelers in finishing and polishing gold, induced Dr. W. Hofiinan 

 to analyze it He found it consisted of seventy per cent of oxide 

 of imu, and thirty per cent of chloride of ammonium (sal ammo- 

 uiae). It is made by subjecting iron to the action of hydi'ochlorio 

 acid. After the hydrogen gas has ceased to escape, a solution of 

 sal ammoniac is added. The precipitate is filtered at a very low 

 temperature to prevent rapid evaporation, 



EFFECT OF ANTISEPTICS ON ANIMALCULE. 



By allowing colpoda, found m vegetable infusions, to come m 

 contact with antiseptics while under the field of the microscope, 

 Dr. Binz, of Bonn, has discovered that two kinds of destructive 

 action ensue. Chloride and hyposulphite of sodium, chlorate of 

 potash and alum, by osmotic action, caused the creatures to burst; 

 while a directly poisonous action was produced by nitric, sulphuric, 

 acetic, and tannic acids, permanganates, creosote, corrosive subli- 

 mate, quinia, chlorine, bromine and iodine. Acetic acid andquinia 

 produced the most powerful effect. Neither salacin nor nitrate of 

 strychnia exerted any immediate influence. 



SOLIDIFICATIOil OF BISMUTH. 



Mr. Alfred Tribe has been experimenting with bismuth, to 

 ascertiiin the correctnc^ of Professor Tyndall's statement, that the 

 anomalous ex|3ansion of water in the a«t of cooling below 4 degrees 

 C, or 30.2 Fah., is by no means an isolated mstance of the kind, 



fiNST.] 57 



