Studies of Quartz Crystals 233 



pronounce it impossible, because carbonate of lime is de- 

 posited as rounded concretions in the presence of mucilage, 

 and the chemical conditions inside a cocoa-nut do not seem 

 to differ essentially from those under which a pearl is formed 

 in the pearl oyster. 



Nov. 24th, 364*11 meeting. Professor Maskelyne exhibited 

 a new electric lamp which had been tried with complete 

 success in the Yorkshire collieries. Its weight is 4 pounds 

 2 ounces, and it gives a light of i^ candle-power, which is 

 maintained by a secondary battery of novel form, the 

 positive being zinc, the negative a special preparation without 

 metallic lead. The lamp shown could run with undiminished 

 light for 9 hours. The glow burner is protected by a dome 

 of toughened glass. This, when broken, flies into fragments, 

 releasing a spring which cuts off the current and instan- 

 taneously extinguishes the light. The lamp had been tested 

 successfully in the most explosive gases of the Yorkshire 

 collieries. 



Dec. I5th, 365th meeting. Professor Judd gave the 

 results of his recent studies of quartz crystals. A lamellar 

 structure has been proved to be developed by strain in many 

 minerals, and Leydolt and Descloiseaux have shown quartz 

 crystals to be built up of lamellae having different properties, 

 the latter observer having demonstrated that the Airy's 

 spirals, exhibited by equatorial sections of such crystals, are 

 due to the overlapping of lamellae of right-handed and 

 left-handed quartz. He exhibited a specimen showing an 

 intergrowth of two left-handed individuals. An equatorial 

 section of this, when etched by hydrofluoric acid, exhibited 

 lamellae, which, with a polariscope and convergent rays, gave 

 Airy's spirals, but further examination showed this lamellar 

 structure to be restricted to parts of the crystals which had 

 been subjected to deforming strain. We were therefore 

 justified in inferring that lamellar structure could be 

 developed by mechanical means in quartz as in calcite and 

 many other minerals. 



1888. Jan. igth, 366th meeting. Professor Newton 

 referred to the discussion on edible bird's nests on Nov. 27th, 



