200 AXNUAL OF SCIENTIFIC DISCOVERT. 



cannot bo destroyed, a mixturo of powdered chloride of zinc, or 

 l>n\v(l('ri'd snlpli.itc of zinc with sawdust, is best. A niixtiu'c of 

 carlioiic aciil aiul sawdust ranks next in order; and, following 

 on tiiat, wood-ashes. 



7. For tlie dcodorizalion and disinfection of infected articles of 

 clothiu"^, etc., exposure to lu'at at 212° Fahr. is the only true 

 methixf. 



8. For the deodorization and disinfection of substances that 

 may be destroyed, heat to destruction is the only true method. 



COMPOSITION OF ANCIENT MORTAKS. 



The composition of ancient mortars has been examined bj' Dr. 

 Wallace, ami the results <i;iv( ii in tiie •• (Mieniicai News." The first 

 specimen was from the great jjyramid, and jircsented the apjx-ar- 

 ance of a mixture of plaster, of a slight pinkisii color, with gypsum. 

 It did not appear to contain any sand, the i»lac(^ of which was taken 

 by coarsely-gntund gypsum. Large quantities of this material and 

 of alaijaster are stateil by Prof. Smyth to be found in tlie vieinit}'. 

 Analysis showed this mortar to contain 82 per cent, of hydrated 

 sulphate of lime, and 'Ji per cent, of carbonate of lime, besides 

 smaller (piantities of other hodies. A very anei(-ut mortar, sup- 

 ]>osed to be the most ancient in existence, was obtained from the 

 ruins of a temple near Larnaca, in Cvj^rus, The temple is now 

 wholly below the ground ; still the mortar was excecclingl}- hard 

 and lirm, and appeared to liave been made of a mixtun; of hurnt 

 lime, sharp sand, and gravel. This mortar contained ehielly 20. 4 

 per cent, of lime, 20.2 of carbonic acid, 16.2 of silica, and nearly 

 29 per cent, of small stones, the lime being almost completely 

 carbonated. Ancient Greek mortars showed somewhat the same 

 composition. Ancient Roman mortars differed, however, being 

 evidently prepared by mixing with burnt lime, not sand, but 

 puzzeolana, or what is commonly, although impropin-ly, called 

 volcanic ash. ■ From all his analyses. Dr. AV'allace deduces the 

 following conclusions : That in the course of time the lime in 

 plasters and mortars becomes completely carbonated ; that where 

 the mortar is freely exposed to the weather, a certain j^i'oportioa 

 of alkaline or earthy silicate is formed, which proliably confers 

 hai'dness, as those mortars are the hardest which have been long 

 below ground. It is known that those walls are strongest which 

 arc; built during the rainy season, as then a small projiortion of 

 silicate of lime is formed, which not only makes the, mortar itself 

 harder, but causes it to unite more firmly with the stone. The 

 mortar which is probably the most ancient is by fiir the hardest, 

 ajipearing like concrete. Its excellence seems to indicate that a 

 large-grained sand is best for building purposes ; and that even 

 small gravel may, in certain cases, be used with advantage. 



COMPOSITION OF CAST-IRON. 



Xot only as a curiosity, but as a matter of profound interest to 

 chemical and technical science, Prof. Remigius Fresenius of VVies- 



