November 30, 1899] 



NATURE 



[09 



volume of air free from all currents and a cubic centi- 

 metre of water free from all impurities, are both of them 

 well-nigh equally difficult of realisation. The exact de- 

 termination of such constants is nevertheless of the 

 greatest scientific interest, and even- the difference be- 

 tween their values and those obtained under more normal 

 conditions affords a measure of the allowance that must be 

 made for the discrepancies which exist between theory 

 and practice. 



Canovetti's experiments, on the other hand, are 

 essentially of the rough and ready order in several 

 respects. The wire hanging as it does in a catenary, the 

 differences of inclination at different parts of the course 

 render the motion far from uniform over the 280 metres, 

 and the estimated velocities can only be regarded as 

 average velocities in a motion with variable velocity, the 

 details of which have not been fully investigated. A 

 further source of error is due to the sagging of the wire at 

 the point where the trolley rests on it, and the consequent 

 absorption of energy in producing vibrations. It is thus 

 not surprising to find that Canovetti obtains 90 grammes 

 for the resistance of a rectangle where Le Dantec finds 

 81 grammes ; one might not unreasonably have expected 

 a greater discrepancy. Although Canovetti avoided 

 windy days, yet his experiments were conducted in the 

 open air under conditions which might be regarded as 

 normal in ordinary calm weather, and so far as the re- 

 sults bear on the question of the relative efficacies of dif- 

 ferent forms of balloons and other bodies in overcoming 

 air resistance, they may be regarded as furnishing data 

 of considerable practical value. G. H. Bryan. 



DR. HENRY HICKS, F.R.S. 

 DRITISH geology suffers a severe loss in the death of 

 -*-' Dr. Henry Hicks, a loss which will long be felt on 

 personal as well as scientific grounds. His chief work was 

 in South Wales, among the older Palaeozoic formations, 

 whose life-history was previously but little known. He 

 pushed his inquiries into the very oldest pre-Cambrian 

 rocks, both in Wales and Scotland ; and then turning 

 from these most ancient records he gave attention to 

 those immediately preceding the present order of things, 

 and pursued with equal ardour the evidences of glacia- 

 tion in South Wales and Middlesex, the records of old 

 bone-caves, and the remains of mammoth in the Thames 

 Valley. No man had a keener eye for fossils. To him 

 rocks which had for long been deemed unfossiliferous 

 yielded up some evidences of life. 



Now and again his enthusiasm led him to draw conclu- 

 sions and express opinions that were too slenderly sup- 

 ported by evidence, and consequently he was brought 

 perhaps more than any other man of his time into active 

 conflict on the battle-field of geology. No one, however, 

 seemed to enjoy more heartily the animated debates 

 which his own papers so often provoked than Dr. Hicks. 



Henry Hicks was born at St. David's, in Pembroke- 

 shire, in 1837, and was educated at the Collegiate and 

 Chapter School in that city. Coming to London to 

 study for the medical profession, he entered Guy's 

 Hospital, and was admitted a Member of the Royal 

 College of Surgeons and a Licentiate of the Society of 

 Apothecaries in 1862. Returning then to his native place 

 he commenced a practice which he continued until 1871, 

 when he removed to Hendon. He now devoted special 

 atention to mental diseases, took the M.D. degree at St. 

 Andrews in 1878, and continued his active and useful 

 medical work until the close of his life. 



It was in 1863, while resident at St. David's, that Dr. 

 Hicks' attention was first attracted to geology, and the 

 inspiration came through the late J. W. Salter, then 

 palaeontologist to the Geological Survey. In the previous 

 year Salter had himself discovered, for the first time in 



NO. 1570, VOL. 61] 



Britain, remains of the large Trilobite Paradoxides, 

 which was then stated to occur in the " Lower Lingula 

 Flags," of St. David's. Dr. Hicks' interest was aroused ; 

 he diligently commenced to search for fossils among the 

 old rocks around him, and as he himself has told, the 

 enthusiasm with which every new find was welcomed by 

 Salter, "to whom they were first sent, was in itself a 

 sufficient stimulus for any exertions required." A grant 

 in aid was received from the British Association in 1863, 

 and in the following year Salter was enabled to report 

 at the Bath meeting that the energetic work of Dr. Hicks 

 "has already brought to light more than thirty species of 

 fossils, most of them Trilobites " ; and as he elsewhere 

 remarked, these discoveries *' made a large addition to 

 the Primordial fauna." 



With the help and encouragement thus given by Salter 

 Dr. Hicks pursued his work with unflagging devotion. 

 His first communication to the Geological Society was 

 made in 1865, and dealt with the genus Anopolenus ; and 

 from that date onwards for some years he contributed a 

 series of most important papers on the stratigraphy and 

 palaeontology of the Cambrian and Lower Silurian rocks 

 of South Wales, two or three of the earlier papers in 

 conjunction with Salter or Robert Harkness. These re- 

 searches led to the establishment of the Menevian group 

 in 1865 by Salter and Hicks for part of the Middle 

 Cambrian division which is characterised by Paradoxides 

 Davidis &c. 



In 1876 he communicated a more particular account 

 of the pre-Cambrian rocks of Pembrokeshire, and here 

 he came perhaps more into conflict than on any previous 

 occasion. The granitoid rock which he named Dimetian 

 and claimed as pre-Cambrian was regarded by Sir A. 

 Ramsay as metamorphosed Cambrian, and afterwards 

 by Sir A. Geikie as a granite mass intruded into the 

 Cambrian rocks. The Pebidian volcanic series, also 

 regarded as pre-Cambrian by Dr. Hicks, was grouped 

 with the Cambrian by Sir A. Geikie. The evidence for 

 a third and intermediate series named Arvonian by Dr. 

 Hicks was subsequently admitted by him to be in- 

 conclusive. In his views concerning the antiquity of 

 the Dimetian, Dr. Hicks was strongly supported by 

 Prof. Bonney, Prof. Hughes and Mr. Thomas Davies. 

 With regard to the Pebidian, it is now recognised that 

 the beds are of the type of the Uriconian of Shropshire, 

 generally classed as pre-Cambrian. 



Between 1878 and 1883, Dr. Hicks published a series 

 of papers on the metamorphic and overlying rocks of 

 parts of Ross-shire and Inverness-shire, with petrological 

 notes by Prof. Bonney and Mr. T. Davies. 



Since he went to reside at Hendon, Dr. Hicks gave 

 much attention to the local geology, and recorded many 

 facts of interest. In course of time the subject of bone- 

 caves greatly occupied him, and Cae Gwyn Cave in 

 particular was explored in company with Mr. E, B. 

 Luxmoore and others. It was then shown that this 

 Denbighshire cavern was occupied by an early Pleistocene 

 fauna and by man before the deposition of any of the 

 local glacial deposits. 



In 1890 Dr. Hicks bent his steps into North Devon, 

 and was much struck with the evidences of folding, 

 faulting and crushing near Ilfracombe. He then for the 

 first time found a Lingula in the Morte Slates, and ex- 

 pressed the opinion that these rocks were older than the 

 Devonian. Working zealously in Devonshire, and re- 

 visiting South Pembrokeshire for the sake of comparisons, 

 he elaborated his views in 1896 and 1897. He had now 

 succeeded in finding a number of fossils in the Morte 

 Slates and in different localities, but whether these were 

 in part true Silurian fossils as maintained by Dr. Hicks 

 and the Rev. (i. F. Whidborne, or wholly Lower 

 Devonian, Dr. Hicks had clearly shown that the suc- 

 cession across North Devon was not continuous and un- 

 broken as had been supposed. The discovery of the 



