ONE:237CHAPTER XIII. SECOND SIGHT.
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ONE:As a means for transmitting power, shafts afford the very important advantage that power can be easily taken off at any point throughout their length, by means of pulleys or gearing, also in forming a positive connection between the motive-power and machines, or between the different parts of machines. The capacity of shafts in resisting torsional strain is as [46] the cube of their diameter, and the amount of torsional deflection in shafts is as their length. The torsional capacity being based upon the diameter, often leads to the construction of what may be termed diminishing shafts, lines in which the diameter of the several sections are diminished as the distance from the driving power increases, and as the duty to be performed becomes less. This plan of arranging line shafting has been and is yet quite common, but certainly was never arrived at by careful observation. Almost every plan of construction has both advantages and disadvantages, and the best means of determining the excess of either, in any case, is to first arrive at all the conditions as near as possible, then form a "trial balance," putting the advantages on one side and the disadvantages on the other, and footing up the sums for comparison. Dealing with this matter of shafts of uniform diameter and shafts of varying diameter in this way, there may be found in favour of the latter plan a little saving of material and a slight reduction of friction as advantages. The saving of material relates only to first cost, because the expense of fitting is greater in constructing shafts when the diameters of the different pieces vary; the friction, considering that the same velocity throughout must be assumed, is scarcely worth estimating.By examining the history of great achievements in the mechanic arts, it will be seen that success has been mainly dependent upon predicting future wants, as well as upon an ability to supply such wants, and that the commercial value of mechanical improvements is often measured by conditions that the improvements themselves anticipate. The invention of machine-made drills, for example, was but a small matter; but the demand that has grown up since, and because of their existence, has rendered this improvement one of great value. Moulded bearings for shafts were also a trifling improvement when first made, but it has since influenced machine construction in America in a way that has given great importance to the invention.
ONE:As a means for transmitting power, shafts afford the very important advantage that power can be easily taken off at any point throughout their length, by means of pulleys or gearing, also in forming a positive connection between the motive-power and machines, or between the different parts of machines. The capacity of shafts in resisting torsional strain is as [46] the cube of their diameter, and the amount of torsional deflection in shafts is as their length. The torsional capacity being based upon the diameter, often leads to the construction of what may be termed diminishing shafts, lines in which the diameter of the several sections are diminished as the distance from the driving power increases, and as the duty to be performed becomes less. This plan of arranging line shafting has been and is yet quite common, but certainly was never arrived at by careful observation. Almost every plan of construction has both advantages and disadvantages, and the best means of determining the excess of either, in any case, is to first arrive at all the conditions as near as possible, then form a "trial balance," putting the advantages on one side and the disadvantages on the other, and footing up the sums for comparison. Dealing with this matter of shafts of uniform diameter and shafts of varying diameter in this way, there may be found in favour of the latter plan a little saving of material and a slight reduction of friction as advantages. The saving of material relates only to first cost, because the expense of fitting is greater in constructing shafts when the diameters of the different pieces vary; the friction, considering that the same velocity throughout must be assumed, is scarcely worth estimating.By examining the history of great achievements in the mechanic arts, it will be seen that success has been mainly dependent upon predicting future wants, as well as upon an ability to supply such wants, and that the commercial value of mechanical improvements is often measured by conditions that the improvements themselves anticipate. The invention of machine-made drills, for example, was but a small matter; but the demand that has grown up since, and because of their existence, has rendered this improvement one of great value. Moulded bearings for shafts were also a trifling improvement when first made, but it has since influenced machine construction in America in a way that has given great importance to the invention.
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ONE:"You know too much," she said quietly. "If that fool Giuseppe had done his duty you would have gone down to your drunkard's grave in ignorance. But you are not going on the Continent tomorrow or the next day. Fool, fool, have you not lived long enough to know that all that glitters is not gold! For the moment I am living on my reputation and the splendour of this house. Not one penny have I paid for it. People hold documents and title deeds of mine that are forgeries. I have a grand coup that may come off, and again it may fail. For the moment I am penniless."The invention is now complete, and as the principles are all within the scope of practical mechanism, there is nothing left to do but to devise such mechanical expedients as will carry out the principles laid down. This mechanical scheming is a second, and in some sense an independent part of machine improvement, and should always be subservient to principles; in fact, to separate mechanical scheming from principles, generally constitutes what has been called chance invention.
ONE:"You know too much," she said quietly. "If that fool Giuseppe had done his duty you would have gone down to your drunkard's grave in ignorance. But you are not going on the Continent tomorrow or the next day. Fool, fool, have you not lived long enough to know that all that glitters is not gold! For the moment I am living on my reputation and the splendour of this house. Not one penny have I paid for it. People hold documents and title deeds of mine that are forgeries. I have a grand coup that may come off, and again it may fail. For the moment I am penniless."The invention is now complete, and as the principles are all within the scope of practical mechanism, there is nothing left to do but to devise such mechanical expedients as will carry out the principles laid down. This mechanical scheming is a second, and in some sense an independent part of machine improvement, and should always be subservient to principles; in fact, to separate mechanical scheming from principles, generally constitutes what has been called chance invention.
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ONE:The traction of belts upon pulleys, like that of locomotive wheels upon railways, being incapable of demonstration except by actual experience, for a long time hindered the introduction of belts as a means of transmitting motion and power except in cases when gearing or shafts could not be employed. Motion is named separately, because with many kinds of machinery that are driven at high speedsuch as wood machinesthe transmission of rapid movement must be considered as well as power, and in ordinary practice it is only by means of belts that such high speeds may be communicated from one shaft to another.
ONE:The traction of belts upon pulleys, like that of locomotive wheels upon railways, being incapable of demonstration except by actual experience, for a long time hindered the introduction of belts as a means of transmitting motion and power except in cases when gearing or shafts could not be employed. Motion is named separately, because with many kinds of machinery that are driven at high speedsuch as wood machinesthe transmission of rapid movement must be considered as well as power, and in ordinary practice it is only by means of belts that such high speeds may be communicated from one shaft to another.
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ONE:In England, the most generally accepted method seems to be that followed by Grote. This consists in taking the Platonic Apologia as a sufficiently faithful report of the defence actually made by Socrates on his trial, and piecing it on to the details supplied by Xenophon, or at least to as many of them as can be made to fit, without too obvious an accommodation of their meaning. If, however, we ask on what grounds a greater historical credibility is attributed to the Apologia than to the Republic or the Phaedo, none can be offered except the seemingly transparent truthfulness of the narrative itself, an argument which will not weigh much with those who remember how brilliant was Platos talent for fiction, and how unscrupulously it could be employed for purposes of edification. The Phaedo puts an autobiographical statement into the mouth of Socrates which we only know to be imaginary because it involves the acceptance of a theory unknown to the real Socrates. Why, then, may not Plato have thought proper to introduce equally fictitious details into the speech delivered by his master before the dicastery, if, indeed, the speech, as we have it, be not a fancy composition from beginning to end?
ONE:In England, the most generally accepted method seems to be that followed by Grote. This consists in taking the Platonic Apologia as a sufficiently faithful report of the defence actually made by Socrates on his trial, and piecing it on to the details supplied by Xenophon, or at least to as many of them as can be made to fit, without too obvious an accommodation of their meaning. If, however, we ask on what grounds a greater historical credibility is attributed to the Apologia than to the Republic or the Phaedo, none can be offered except the seemingly transparent truthfulness of the narrative itself, an argument which will not weigh much with those who remember how brilliant was Platos talent for fiction, and how unscrupulously it could be employed for purposes of edification. The Phaedo puts an autobiographical statement into the mouth of Socrates which we only know to be imaginary because it involves the acceptance of a theory unknown to the real Socrates. Why, then, may not Plato have thought proper to introduce equally fictitious details into the speech delivered by his master before the dicastery, if, indeed, the speech, as we have it, be not a fancy composition from beginning to end?
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ONE:Leona Lalage swept into her box later on with the air of one who feels that she is the centre of all attraction. Society was charmed and gratified, distinguished men dropped into the box on the grand tier, and whispered their congratulations. The brilliant stream of diamonds in her hair was no brighter than the woman's eyes.He bought one eagerly enough, and stood spellbound on the pavement whilst he read. It was all here, even down to a signed copy of the confession. Lawrence had seen to that. Bruce turned into his club in a dazed kind of way. The smoking-room was full, he was the centre of a group, all of which seemed eager to shake hands. It was all so sudden that Bruce was not himself yet.
ONE:Leona Lalage swept into her box later on with the air of one who feels that she is the centre of all attraction. Society was charmed and gratified, distinguished men dropped into the box on the grand tier, and whispered their congratulations. The brilliant stream of diamonds in her hair was no brighter than the woman's eyes.He bought one eagerly enough, and stood spellbound on the pavement whilst he read. It was all here, even down to a signed copy of the confession. Lawrence had seen to that. Bruce turned into his club in a dazed kind of way. The smoking-room was full, he was the centre of a group, all of which seemed eager to shake hands. It was all so sudden that Bruce was not himself yet.
THREE:"All right; you may go!""Even you are puzzled, uncle," Hetty said to Lawrence. She was off for the afternoon; she had called at the novelist's chambers to meet Bruce there with an eye to a little shopping and a visit to the new house in Green Street. "I know you are interested. Can't you make anything out of it?"
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