SUMMARY OF RESULTS. 
63 
within a mile of Sienna, there existed a bed of microscopic shells analogous to those 
found on the shores of Rimini. 
Later on, Soldani examined with a magnifying glass the clay of the tufa and sands of .Soumni. 
North Italy, and produced his essay on the nautiloid layers of Tuscany, 1 and thus enriched 
science with descriptions and drawings of a multitude of shells belonging to minute 
marine animals, always looked upon as nautili and ammonites, an error perpetuated till 
1835. As he assigned no particular names to these diversified forms, which he described 
and represented with care, and even grouped according to certain analogies, Soldani did 
not contribute to advance the knowledge of them as much as he might have done had 
he applied to them the then well-known nomenclature of Linnaeus. From 1789 to 1797 
he published another very considerable work 3 on the microscopic shells found on the 
shores of Giglio, Elba, and other islands. He observes in this work that these 
small bodies are not young specimens, which grow with age, but perfect adults ; the 
various species occupy various depths, and this explains, he adds, why those in a fossil 
state are not found mixed indifferently in all the strata. 
The hypothetical ideas of some Arab writers, and the observations of Pytfieas and Progress <n 
Posidonius on the causes of tides have been already noticed. 3 In the sixteenth century 
there was marked progress in the knowledge of these phenomena ; men began to Tides. 
study the local peculiarities of the tides, as shown by the instructions given by Cabot 
for the Polar explorations (1553), according to which the time when a particular 
tide set in was to be noted down for each port. It was owing to observations of 
this nature that a body of facts was gradually grouped together on which to 
establish the theory of tidal phenomena. Galileo connected them with the rotation of 
the earth on its axis ; Francis Bacon found their explanation in the configuration of 
the terrestrial masses of the Old and Nev r Worlds. Simon Stevin is nearer the truth, 
for he can already foretell for each port the hour of the tide by means of lunar phases. 
Kepler, in the Introduction to his Astronomia Nova, recognises the dependence of the 
tides on the attraction of all the heavenly bodies. Descartes came next with his theory 
of the eddies of ether, which Varenius accepts as being the best explanation of the 
phenomena of flux and re-flux. Lastly, the publication of Newton’s Principia pro- 
duced a complete modification in this branch of science, and the works of MacLaurin, 
Euler, and Bernouilli, competing for the prize offered by the Academy of Sciences of 
Paris in 1740, added new mathematical elements to the theoretical ideas of the time. 
Observations on marine currents increased as people began to abandon coa-ting, 
1 Saggio orittografieo ovvero osservazioni sopra le terre nautilitiche ed ammonitiche della Toscana, Siena, 17S0. 
- Testaceographia et zoophytographia parva et microscopiea [4to, with 179 plates], Siena, 1789-1797 (cited 1 y 
d ! Arehiac). 
3 See pp. 15, 21, 37. 
