Another name that must be linked with those already mentioned in connection with the change from wood to iron in shipbuilding, and with the new conditions imposed by the transition from sail to steam, is that of the late Mr John Scott Russell, already referred to at the beginning of this work. In the fields of inquiry so largely opened up at the period referred to, Mr Russell was a most distinguished worker. His advocacy and adoption in practice of special structural principles, as illustrated not only in the _Great Eastern_ but in other vessels, has influenced subsequent practice incalculably, and by his persevering investigations upon the resistance of vessels, and the “wave-line” theory he advanced, as well as by his inquiry into the characteristics of wave motion, he laid designers of that period and subsequent investigators under great indebtedness. His contributions to the literature of the profession—notably his _magnum opus_, entitled “Modern System of Naval Architecture”—and the large share he subsequently took in the deliberations of the Institution of Naval Architects, and of other societies concerned with shipbuilding and engineering, enhance that indebtedness and remain as permanent records of his skill and originality. Approaching the period with which this review is more particularly concerned, reference must now be made to the valuable labours of two eminent men, whose loss the profession has had to mourn within recent years. These are the late Professor Macquorn Rankine and the late Mr William Froude, neither of whom was by profession a naval architect, yet both of whom were led by love of the subject to give their matured experience as civil engineers and mathematical experts to the promotion of knowledge in this domain.