PREFACE. Xlll 



numerous experiments made to determine the mechanical properties of 

 Indian timbers, the results of those only which relate to transverse 

 strength have been given. P. is the constant represented by the follow- 

 ing well-known formula : 



L x W 



P = 



d 2 



L being the length in feet of the scantling tested between supports 

 (bearing length), W the weight producing fracture of the scantling loaded 

 in the middle, b breadth of scantling in inches, d depth of scantling in 

 inches. 



It now remains briefly to narrate the history of this work, to enumer- 

 ate the materials upon which it is based, and to acknowledge the assist- 

 ance received during its preparation. In 1869, the late Dr Stewart, 

 then Conservator of Forests in the Panjab, came home on furlough, and 

 the Government of India intrusted him with the preparation at Kew of 

 this work, for which he had been collecting materials for several years. 

 While officiating in 1860-61 for Dr Jameson as Superintendent of the 

 Botanic Garden at Saharanpur and of the Government Tea Plantations 

 in the North- West Provinces, and subsequently while Civil Surgeon at 

 Bijnaur in Rohilkhand, he became familiar with the forest vegetation 

 in the plains and in the Himalaya between the Jumna and Kali rivers. 

 In 1864 he returned to the Panjab, where he had passed his first years 

 of medical service, principally on the western frontier, and being then 

 appointed to the charge of the forests in that province, he devoted the 

 greater part of his time to the botanical exploration of the Panjab Hima- 

 laya, Kashmir, and the adjoining districts of Tibet, and to repeated care- 

 ful examinations of the Rakhs and brushwood tracts in the plains west of 

 the Jumna river, including the adjoining province of Sindh. He thus 

 acquired an extensive knowledge of the forest vegetation of a large 

 portion of North -West India, and the copious notes taken on the spot in 

 all his travels contained a rich store of information. In order to enable 

 him to include the forest vegetation of Oudh and the Central Provinces, 

 a forest officer of the North- West Provinces, Mr Richard Thompson, who 

 had formerly served under Dr Stewart at Saharanpur, was at his sugges- 

 tion deputed to visit the principal forest tracts of those provinces ; and the 

 notes and collections made by that officer were sent to him at Kew. Dr 

 Stewart's previous publications in various scientific journals, as well as 

 the numerous and valuable official reports submitted by him as Conserva- 

 tor of Forests, and his excellent book on the " Useful Plants of the Panjab," 

 fully warranted the expectation that, after the needful preparatory study at 

 home, he would be equal to the important task intrusted to him. He accord- 

 ingly devoted a large part of his furlough, from 1869 to 1871, to this work, 



