M. Martin on the Amylum Gravis of the Potatoe. 277 



3Si0 3 + 6H 2 0; epistilbite, RO, Si0 3 +Al 2 3 , 3Si0 3 + 5H 2 0. 

 Appendix :— Okenite, 3CaO, 4Si0 3 + 6H 2 0. 



Heulandite Type : — Monoclinic. 



Datolite, 6CaO, 4Si0 3 , 3B0 3 , 3H 2 0, or (botryolite) 6H 2 0; 

 laumonite, 3CaO, 2Si0 3 + 4(Al 2 3 , 2Si0 3 ) + 18H 2 = a mo- 

 noclinicphillipsite; leonhardite, 3(CaO, SiO 3 ) +4(A1 2 3 , 2Si0 3 ) 

 + 15H 2 Ojbrewsterite,(SrO,BaO),Si0 3 + Al 2 3 ,3Si0 3 4-5H 2 0; 

 heulandite (stilbite of German authors), 3(CaO, SiO 3 ) + 4(A1 2 3 , 

 3Si0 3 ) + 18H 2 0. 



XXXIX. On the Amylum Grains of the Potatoe. By A. G. C. 

 Martin, Librarian of the Imperial Polytechnic Institute of 

 Vienna*. 



[With a Plate.] 



FOR some time past I have been engaged in investigating 

 the phenomena which occur when the amylum grains of 

 the potatoe arc subjected to the action of boiling water, and I 

 have discovered a new fact which is not in accordance with the 

 present theory and prevailing notions concerning their structure. 



Although there is in microscopical observations great liability 

 to erroneous conclusions, and consequently extreme caution ne- 

 cessary at every step, still too much timidity would speedily put 

 a stop to the progress of science, and hence I trust that the 

 scientific world will consider my numerous experiments worthy 

 of being submitted to a trial. 



Prior to commencing my experiments, I made myself thoroughly 

 acquainted with all that had been written on the subject of amy- 

 lum t, and found that in no instance was there any detailed 

 account of the phenomena presented in the formation of amylum 

 or the process of boiling. This is easily accounted for by the 

 fact, that precisely at the above point our knowledge ceases. The 

 object of my researches was to supply this defect. 



1. The microscope I employed is one by Plossl. Most of my 

 observations were made with the object-glasses Nos. 3, 4 and 

 5, and the eye-glass No. 2, a combination which gives a magni- 

 fying power of 198 diameters. Plossl, in his recent microscopes, 

 has made the reflector moveable outside the axis, by which an 



* Communicated by the Author. 



t Fritsche on Amylum, Poggendorff's Annalen, vol. xxxii. p. 129. Mohl, 

 Anatomy and Physiology of Vegetable Cells, p. 48. Payen, Practical Che- 

 miatry, p. 347< Regnault, Elements of Chemistry, vol. iii. p. 161. Schleiden, 

 Elements of Scientific Botany, tirst edition, p. 1/1. Schleiden and Schmidt) 

 Encyclopaedia of Natural Science, vol. iii. p. 33. Unger, Anatomy and 

 Physiology of Plants, p. 3'J. 



