112 Rev. W. D. Conybeare on the alleged 



tached to the upper side of the sexual organs, the longer con- 

 nected with the same organs on the inner side and extending 

 beyond them. The sexual organs are glossy, of a globular 

 form, with a pointed elongation anteriorly; their colour is 

 dark reddish-brown, approaching to black. 



This spider, which was discovered by Mr. T. Blackwall in 

 September 1831, under stones and rubbish in the township of 

 Crumpsall, pairs in the month of October. In it are com- 

 bined several striking characteristics of the genera Theridion 

 and Tetragnatha. Allied to the former by the structure of 

 the mouth, and the irregularity of the insignificant web it fa- 

 bricates, it resembles the latter in the form and relative length 

 of the legs, which it frequently extends in the same manner as 

 Tetragnatha extensa; thus closely connecting by its organiza- 

 tion and ceconomy the Inequitelce with the Orbitelce. 



Oaklamb, near Llanwrst, Denbighshire, 

 July 12th, 1833. 



XXII. On the alleged Discovery of Coal at Billesdon, Leices- 

 tershire. By the Rev. W. D. Conybeare, M.A. F.R.S. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



f NthelastNumberofyour valuable Journal, (p. 76) is a "Notice 

 -*• of the Discovery of Coal-measures at Billesdon, Leicester- 

 shire," which strongly illustrates the misunderstanding, so much 

 to be regretted, that is often found to prevail in the minds of 

 those engaged in practical researches, with regard to those gene- 

 ralized views qf science, which are the only guides of really effective 

 inquiries, but which are by such persons hastily thrown aside, 

 under the entire misconception that they are founded only on 

 data purely theoretical; whereas, in fact, the general views 

 of systematic science are necessarily, wherever they are just, 

 founded primarily on an extensive induction from practical 

 observation, and from practical observation alone. They pre- 

 sent, indeed, merely the combined and condensed results of 

 the very widest practical observation, — divested only of the 

 very obvious cause of error which a narrow spirit of judging 

 from mere local acquaintance with a single district must ne- 

 cessarily introduce. 



Thus in the notice which has occasioned these remarks, 

 Mr. Holdsworth announces the discovery of coal-measures at 

 Billesdon, without anything like a precise description of the 

 thickness, range or extent of a single bed of coal; and relying 

 only on washing from the materials produced by boring; 



