XIV INTRODUCTION. 



The rate of growth is recorded as " slow ", " moderate ", or " fast ", 

 according as the number of rings per inch is greater than 12, between 12 

 and 6, and less than 6. These correspond to ages at 6 feet in girth of 

 134 years, 67 to 134, and 67 years respectively. 



Weight. As already stated in reference to the annual rings, the ex- 

 periments made with our specimens in ascertaining the specific gravity 

 of different kinds of woods, are also merely given as being often the only 

 information available. Most of the specimens weighed were of small size, 

 and they were, perhaps, not always cut so as to be capable of very exact 

 measurement, but, nevertheless, the information obtained is of value and 

 can serve until it is supplemented or superseded by more accurate experi- 

 ments made with a large choice of specimens. 



The weighings were done by Mr. Smythies and Dr. H. Warth, and 

 the result is given in the form of the number of pounds per cubic foot, as 

 being a more easily utilized form of information than the figures repre- 

 senting the specific gravity, compared with that of water taken as 1. 

 The weight here recorded is always, unless otherwise stated, that of sea- 

 soned timber, and it is given as " light", ".moderately heavy", " heavy '% 

 and i{ very heavy " according as the woods give :- 



Light, less than 301bs. per cubic foot. 



Moderately heavy, from 301bs. to SOlbs. per cubic foot. 



Heavy, from 501bs. to 701bs. per cubic foot. 



Very heavy, over 701bs. per cubic foot. 



As in the Forest Flora of North- West and Central India, only the in- 

 formation regarding the transverse strength of timber is recorded, though 

 in a few cases the modulus of elasticity is also given. 



In regard to transverse strength, the value of P is the result obtained 



by the formula 



w x L 



B x D a 



where 



W=The breaking weight, or the weight which when placed ou the middle of the 



bar causes it to break. 



L=the length of the bar between supports, in feet. 

 B=the breadth of the bar, in inches. 

 D=its thickness, in inches. 



A great number of recorded experiments have been brought together, 

 chiefly from those made by Baker, Skinner, Benson, Bennett, Dundas, 

 and others, while in these pages are for the first time published the re- 

 sults of the valuable and careful experiment* made in Calcutta by Dr. 

 Brandis in 1864. 



