B. TERRESTRIAL PHYSICS AND METEOROLOGY. 119 



has favored the world with a careful summary of the princi- 

 pal points of his profound mathematical work of seven hun- 

 dred octavo pages, the result of twenty-five years' study and 

 practical experience of this subject, from which we make the 

 following extracts : Cialdi has sought, with apparent suc- 

 cess, to apply his results, which are indeed generalizations 

 from long experience and accurate observation, to the benefit 

 of harbors and rivers, etc. ; in the words of Scott Russell, " to 

 force the waves, those dangerous enemies, to become our 

 sturdy slaves." The practical application of his views is 

 now being carried into execution in the mouth of the Izauro, 

 and he hopes also to improve Port Said. 



The author gives first a brief but quite thorougli review of 

 the works of Italian philosophers, beginning with Leonardo 

 da Vinci, and passes then to English, Spanish, and German 

 writers on this subject. He criticises justly all the numer- 

 ous analytical works on this branch, because authors have, 

 by the insufiiciency of mathematical analysis, been obliged to 

 deny the movement of transportation within a wave, w^hich 

 action is shown by observation to be a highly important com- 

 ponent of wave motion ; and he finds that this has been prop- 

 erly considered only in the w^orks of Leonardo da Vinci. Ci- 

 aldi next gives his own studies of the question of the move- 

 ment of the molecules of undulating waves, and the effect of 

 wind on waves, both in the deep sea and near the shore. In 

 the third section of his work he collects all the measurements 

 that have been made of the dimensions and movements of 

 waves, both on the ocean and in the Mediterranean Sea. He 

 also examines minutely the question of the "breaking" of 

 the waves, and finds that the causes of this phenomenon may 

 lie at a depth of six hundred feet in the deep ocean, and at a 

 depth of one hundred and fifty feet in the Mediterranean. It 

 follows from these considerations that sand is elevated from 

 these same depths by the action of waves during storms. 

 Cialdi then analyzes the details of the destructive work of the 

 wave influence even at great depths, as shown in many per- 

 manent sea works, and especially in the breaking up of the 

 frigate Titus^ sunk near Cape Frio, and likewise in the expe- 

 rience of those using diving-bells, which can not be employ- 

 ed with safety in stormy weather at a less depth than sixty 

 feet. He also examines the subject of waves without an ac-^ 



