94 JOHN HILL 



Construction of Timber. In order that other investigators might 

 benefit from his experience he fully described and figured the 

 instruments used ; of particular interest is a small hand micro- 

 tome with which he cut his sections. This ingenious tool was 

 the invention of Cummings, and does not differ in essentials 

 markedly from some the writer has seen in use ; Hill claims that 

 when the cutter was particularly sharp sections no thicker than 

 a 2000th part of an inch could be obtained. The microscope was 

 made by Adams under the- direction of Hill and his patron, 

 unnamed in the book, but in all probability Lord Bute, and 

 embodied some improvements on earlier instruments. This 

 microscope is figured in Carpenter's work on The Microscope 

 and its Revelations^. 



The Construction of Timber is well arranged : the work begins 

 with a general description of the tissues and their disposition in 

 a thickened stem ; then follows a more detailed account of the 

 separate tissues ; and finally much space is devoted to a com- 

 parison of different tissues in various plants. 



Hill's account is fully illustrated with copper plates ; his 

 figures of sections are not highly magnified, some not more than 

 twelve times, and their quality is not equal to the best in Grew's 

 A natomy. 



Hill principally studied transverse sections, and consequently 

 fell into errors which he might have avoided by the careful obser- 

 vation of longitudinal ones; also he used macerated material, but 

 as his method preserved only the stronger walled elements he 

 did not gain to any great extent from their use. 



The parts devoted to comparative anatomy are not at all bad, 

 and they give a concrete idea of the differences obtaining in the 

 different plants. 



He apparently understood the nature of the annual rings, 

 and of them he wrote as follows : " These are the several coats 

 of Wood, added from season to season. It has been supposed 

 that each circle is the growth of a year ; but a careful attention 

 to the encrease of wood has shewn me, beyond a doubt, that two 

 such are formed each year ; the one in the Spring, the other soon 

 after Midsummer." His illustration, however, is not so clear as 



' Ed. by Dallinger, London, 1891. 



