Agradecimentos: The authors wish to thank many people who collaborated with them in pre-vious works related to the topic of this book, and also several others for their support, advice, suggestions, references, etc. In particular they thank Waldyr A. Rodrigues Jr., A. Jamil Mania, Jorge I. Cisneros, Hector T. Silva, João E. Lamesa, Roberto A. Clemente, defonso marnisch., Roberto d. A. Martins, A. M. Mansanares, Edmundo Capelas de Oliveira, Alvaro Vannucci, Iberê L. Caldas, Daniel Gardelli, Regina F. Avila, Guilherme F. Leal Ferreira, Marcelo de A. Bueno, Humberto de M. França, Roberto J. M. Covolan, Sérgio Gama, Haroldo F. de Campos Velho, Marcio A. d. F. Rosa, José Emílio Maiorino, Mark A. Heald, G. Galeczki, P. Graneau, N. Graneau, John D. Jackson, Oleg D. Jefi-menko, Steve Hutcheon, Thomas E. Phipps Jr., J. Paul Wesley, Junichiro Fukai, J. Guala-Valverde, Howard Hayden, Hartwig Thim, D. F. Bartlett, F. Doran, C. Dulaney, Gudrun Wolfschmidt, Karin Reich, Karl H. Wiederkehr, Bruce Sher-wood, Johann Marinsek, Eduardo Greaves, Samuel Doughty, H. Härtel and C. Roy Keys. AKTA wishes to thank Hamburg University and the Alexander von Hum-boldt Foundation of Germany for a research fellowship on "Weber's law applied to eletromagnetism and gravitation." This research was developed at the In-stitut für Geschichte der Naturwissenschaften (IGN) of Hamburg University, Germany, in the period from August 2001 to November 2002, during which he first had the idea to write this book. He was extremely well received in a friendly atmosphere and had full scientific and institutional support from Prof. Karin Reich and Dr. K. H. Wiederkehr. JAH wishes to thank CNPq, Brazil, for financial support. The authors thank also FAEP-UNICAMP for financial support to this project, and the Institute of Physics of the State University of Campinas - UNICAMP which provided them the necessary conditions to undertake the project Ver menos