Modifying the science tree

What do you think of my science tree: What corrections would you make? I disagree with ruptures from age to age, so i did this:

1st degree: Egypt, Babylon, Sumer start with these and Polytheism
Pottery
Masonry
Ceremonial

2nd degree:
Polytheism (Ceremonial)
Bronze (Pottery-Masonry)
Writing (Pottery-Masonry)
Wheel (Pottery-Masonry)

3rd degree:
Warrior Code (Polytheism)
Iron (Bronze)
Horseback (Bronze)
Currency (Bronze, Writing)
Alphabet (Writing)

4th Degree:
Monarchy (Warrior Code)
Mathematics (Alphabet)
Philosophy (Alphabet)

5th Degree:
Code of Laws (Monarchy, Writing)
Construction (Iron, Mathematics, Wheel)
Map Making (Mathematics)
Literature (Philosophy)
Monotheism (Monarchy)

6th Degree:
Republic (Code of Laws, Philosophy)
Engineering (Construction)
Theology (Monotheism, Literature)

7th Degree:
Feudalism (Theology)
Invention (Engineering)

8th Degree:
Chivalry (Feudalism, Horseback Riding)
Printing Press (Invention)
Gunpowder (Invention, Feudalism)

9th Degree:
Education (Printing Press)
Astronomy (Printing Press)

10th Degree:
Banking (Education, Currency)
Chemistry (Education)
Music Theory (Education)
Navigation (Astronomy)

11th Degree:
Economics (Banking)
Metallurgy (Chemistry)
Physics (Chemistry, Astronomy)

12th Degree:
Democracy (Economics, Republic)
Military Tradition (Chivalry, Metallurgy)
Medicine (Physics)
Theory of Gravity (Physics)
Magnetism (Physics)

13th Degree:
Free Artistry (Democracy)
Scientific Method (Medicine)
Steam Power (Metallurgy, Gravity, Magnetism)
Nationalism (Military Tradition)

14th Degree:
Industrialization (Steam Power)
Electricity (Steam Power)

15th Degree:
Sanitation (Scientific Method, Electricity, Industrialization)
Corporation (Industrialization)
Espionage (Nationalism, Industrialization)
Communism (Economics, Industrialization)
Fascism (Nationalism, Industrialization)

16th Degree:
Steel (Corporation)
Refining (Corporation)

17th Degree:
Combustion (Steel, Refining)

18th Degree:
Atomic Theory (Combustion, Scientific Method, Electricity)

I didn't finish yet. Like i said before, i disagree with ruptures between ages.

Well, there is nothing you can do about that.

Eh?
The game works with it, the science graphics may not look good but it still works. I'll try to fit them all into one screen.