320 



NATURE 



[August 6, 1891 



a string into action, it would be necessary to wait till two par- 

 ticles were moving on paths with a common normal — an occur- 

 rence which must be infinitely rare. When Prof. Lodge says 

 "an infinite mass can absorb any amount of momentum, with- 

 out receiving a trace of energy, &c.," he forgets that the term 

 *' infinite " is only relative, " an infinite mass " being one whose 

 change of velocity (or kinetic energy) consequent on a given 

 change of momentum is negligible /t^r the purpose in hand. It 

 would not, I imagine, suit Prof. Lodge's purpose to suppose 

 psychic forces might do a little work, so long as it was only a 

 very little ? 



May I remind him of the old paradox, " What would happen 

 if an irresistible force were brought to bear against an immov- 

 able post ?" Edward T. Dixon. 



12 Barkston Mansions, South Kensington, July 24. 



The discussion on this topic has gained in clearness by Prof. 

 Lodge's conceding that " the same question — What determines 

 the direction of the transfer of energy ? — may doubtless be asked 

 in connection with inanimate activity ; . . . but in neither case 

 do I know the answer." 



Perhaps some more precision may be attained by expressing 

 the question in other words. 



The principle of conservation of energy reigns over the 

 quantitative relations of all processes in nature, but it does not 

 give any explanation of the qualitative changes of those processes. 

 These changes and their conditions must in every case be 

 found out by special experience. But, nevertheless, they are, 

 in every accessible case, found to be subjected to fixed laws. 

 A given substance undergoes evaporation or chemical transform- 

 ation — dependent on or necessarily bound up with changes of 

 heat into energy of molecular motion, or into chemical energy, 

 or vice versA — at a distinct degree of temperature, or under 

 distinct conditions of electrical action. Inexplicable as these 

 transformations of quality or form of energy remain for us, 

 there is nothing undetermined in them, neither have we any 

 right to such a supposition for the qualitative changes going on 

 in plants and animals — their quantitative relations being like- 

 wise governed by the principle of conservation of energy. 



But there is another phase of the question. Some unknown 

 material changes in the brain are connected with phenomena of 

 consciousness. Nothing can be more fallacious than to consider 

 consciousness as a form of energy, and to suppose it in a relation 

 of equivalence to such forms. How it is, that what to our 

 physical conception, or outer sense, are processes in the brain 

 (which, as such, may be more clearly understood in future), are, 

 at the same time, to our psychical conception, or inner sense, 

 phenomena of consciousness, or acts of will, is a question 

 beyond the domain of physical science, and capable of elucidation 

 only by transcendental philosophy. Whoever wishes for more 

 light here, must study the " Kritik der reinen Vernunft," espe- 

 cially the chapters "Von den Paralogismen " and "Die 

 Antinomien." 



Schopenhauer, and others after him, have considered our 

 power of will, or our conscious directing of motion, as the key 

 lor all qualitative processes in nature, these being considered 

 as, in their essence, acts of will. But this is cutting the knot by 

 means of a metaphysical assumption. D. Wetterhan. 



Freiburg, Badenia, July 27. 



In reading over the remarks of Dr. Lodge and Prof. Morgan 

 upon Dr. CroU's views as to the direction of force, it appears to 

 me that both have missed the point. Dr. Croll did not mean 

 that a force at right angles to another does no work, but simply 

 alters the direction. His view is that the change of direction is 

 not caused by a force. Dr. Lodge says it is, although he ac- 

 knowledges that the second force does no work. Further, Dr. 

 Croll says, with regard to the first force, that its direction is 

 quite apart from the force. The force cannot direct itself. 

 This is the crucial point before we get to a second force or to a 

 right angle. I fully acknowledge the importance of Dr. 

 Lodge's principle, but it is not simply the indorsement of 

 Dr. Croll's idea. 



Prof. Morgan thinks Dr. CroU's view no argument in favour 

 of theism. It does not prove that mind can or does affect 

 matter. Perhaps it does not directly prove this, but, within its 

 range, it seems to me an effective reply to mechanical atheism. 

 We see direction, and if this does not come from force it must 



come from some other source. We know of no other source 

 but mind. To talk of mind affecting matter denies the essence 

 of mind by which it is distinct from matter, and makes it a 

 mechanical ab extrd. But try to bani.sh it and it will come in 

 somewhere. " Tamen usque recurret. " 



Dr. Croll's position seems to me to affect the first law of 

 motion. Uniform motion in a straight line is in no way con- 

 nected essentially with force, if his view is correct. 



Dr. Lodge's principle appears to affect the second law of 

 motion, and also the doctrine of impact and transference of 

 force. 



Further, it affects gravity. Gravity is always at right angles 

 to the first law of motion, and therefore gravity is not a force ; 

 for that can not be a force which never exercises force. 



T. Travers Sherlock. 



Congregational Church, Smethwick, July 25. 



Technical Education for Farmers, Farriers, and 

 Engine-Drivers. 



Knowing that you take very great interest in the various 

 questions relating to technical education, I may give you a few 

 particulars of an experiment which the Devon County Agri- 

 cultural Society recently made at its Exmouth meeting. Being 

 desirous of giving farmers, farriers, and those generally interested 

 in the welfare of horses, some information on the scientific prin- 

 ciples which underlie a proper performance 'of the duties of the 

 farrier, and the correct form and mode of attachment of horses' 

 shoes ; and also of giving farmers and engine-drivers some 

 practical and scientific instructions on the working and care of 

 steam-engines, the Society approached the County Council with 

 a view to a grant in aid of their object. The proposal was very 

 warmly taken up by Mr. Lethbridge and other gentlemen who 

 are well known for their active interest in education and other 

 matters important to the welfare of the county, and a grant was 

 obtained. 



The Society secured the services of Prof. F. Smith, head of 

 the Army Veterinary School, Aldershot, and of Mr. W. Worby 

 Beaumont, and by these gentlemen lectures were given on each 

 of the three days of the Society's meeting at Exmouth. The 

 weather was very unfavourable on two days, but notwithstanding 

 this the attendance at the lectures was large, and on the second 

 and third days was larger than was expected, and was fully up 

 to the accommodation provided. The audiences were remarkably 

 attentive and appreciative, and in every respect the experiment 

 proved successful. Many who were sceptical before the lectures 

 of their value to working men, became convinced that not only 

 is it possible to give working men information which is useful in 

 an important degree in their daily work, but that the men are 

 themselves quick to appreciate its value. I may mention that 

 on one of the days nearly two hundred shoeing-smiths and a 

 large number of farmers attended the horse-shoeing lectures, 

 and on one day seventy-eight engine-drivers entered for the 

 lecture on the steam-engine, and there were also in attendance a 

 large number of working and gentlemen farmers. 



Totnes, July 29. John L. Winter. 



THE ERUPTION OF VESUVIUS OF JUNE 7, 

 1891. 



THE suggestion that I published in several newspapers 

 has been fully confirmed — namely, that the second 

 alternative type of eruptive character, would be pursued 

 by the volcano. Now for a period of over a month lava 

 has continued to dribble forth, activity has returned to 

 the central vent, and no great changes have occurred. 



The throat of the volcano commenced to be cleared on 

 June 9, the vapour forcing its way up from the crater 

 bottom through the choke of loose materials, and rose 

 above as a column carrying with it much dust ; at the 

 same time the powerful vapour blast issuing from the 

 upper extremity of the lateral rift, of which mention is 

 made in my first letter, soon stopped. Each day I was 

 kept informed of the state of the volcano by the kindness 

 of Messrs. Ferber and Treiber, the director and engineer 

 respectively of the Vesuvian Railway. 



On June 15 I considered it right to again visit the 



NO. 1 1 36, VOL. 44] 



