Mr. White on Calcareous Cements. 57 



Inferences from the foregoing Experiments. 



It may be inferred from the foregoing experiments, that an im- 

 portant adhesion of brickwork had taken place by the use of Poz- 

 zolano, sand and lime, in the short period of thirty days. 



That from the use of Pozzolano and lime in the proportions spe- 

 cified, almost all the advantages required from a good building 

 cement were obtained. 



That Lord Mulgrave's or Atkinson's cement had, in the short 

 period of twenty-three days produced an induration which was 

 sufficient to maintain almost any weight brickwork was capable of 

 for openings in buildings ; the effect probably would have been the 

 same in Parker's, had the material not set before the bricks were 

 fixed in it, further, that Pozzolano had not, in that period, produced 

 an equal adhesion, and that common mortar had produced hardly 

 any; and it appears from the splitting of the large piers thrown 

 down on the 21st April, that an increasing induration took place ; 

 this was evident from the nearly equal fracture of the bricks and 

 cement. 



The incompressibility of mortar being one of its most material 

 qualities, it results that Parker's, Mulgrave's, and Pozzolano, are so 

 far equally useful, that brickwork composed with them will bear 

 on each superficial foot before the bricks will crack, about twenty- 

 three tons, that fifty tons will totally crush such brickwork ; and 

 that Portland stone, of the best quality, will not split with less 

 than one hundred seventy-three and a half tons, and that a bedding 

 or joint of Pozzolano mortar is not destructible with that weight. 



Art. IX. Remarks on Phytolacca Dodecandra, or, the 

 Mustard Tree of the Scriptures. By John Frost, F.L.S., 

 Member of the Royal Institution, &c. 



[Communicated by the Author.] 

 The remark in the sacred volume *, that a grain of mustard 

 seed should become a tree, must have appeared to many very pa- 



* Luke, chap. 13, ver. 19, " A grain of mustard seed which a man took and 

 cast into his garden : and it grew and waxed a great tree, and the fowls of the 

 air lodged in the branches of it." It 



