A little over 2,200 years ago, the Roman navy attacked the Greek port city of Syracuse. According to some ancient historians, the Greeks defended themselves with an ingenious weapon called a "burning mirror": a polished copper surface curved to focus the Sun's rays onto Roman ships, causing them to catch fire. However, we have several reasons to suspect that the story of the burning mirror is just a myth and the Greeks of Syracuse never really built such a device.
First, the ancient Greeks were not technologically advanced enough to make such a device. A mirror that would focus sunlight with sufficient intensity to set ships on fire would have to be several meters wide. Moreover, the mirror would have to have a very precise parabolic curvature (a curvature derived from a geometric shape known as the parabola). The technology for manufacturing a large sheet of copper with such specifications did not exist in the ancient world.
Second, the burning mirror would have taken a long time to set the ships on fire. In an experiment conducted to determine whether a burning mirror was feasible, a device concentrating the Sun's rays on a wooden object 30 meters away took ten minutes to set the object on fire; and during that time, the object had to be unmoving. It is unlikely that the Roman ships stayed perfectly still for that much time. Such a weapon would therefore have been very impractical and ineffective.
Third, a burning mirror does not seem like an improvement on a weapon that the Greeks already had: flaming arrows. Shooting at an enemy's ships with flaming arrows was a common way of setting the ships on fire. The burning mirror and flaming arrows would have been effective at about the same distance. So the Greeks had no reason to build a weapon like a burning mirror.
In the lecture, the professor disagrees with the opinion that the Greeks do not use the burning mirror as a weapon, which contradicts the reading's point of view.Primarily, the lecturer suggests that the mirror can be made of several pieces of copper sheet instead of single one. When arranged together, the copper can be effective. Whereas in the passage, the author strongly believes advanced technology was not available by then.
Secondly, the professor uses the material pitch to disprove the hypothesis in the passage. In order to make the ship water tight, special material are used, namely the pitch. However, pitch is relatively combustible and can start a fire in seconds. Therefore, when caught on a fire, the pitch can spread the fire to the wood, thus giving rise to the burning of the ship. Hence, the burning mirror can be an effective weapon.
Last but not least, the professor lists the fact that the Roman navy were familiar with flaming arrow. Consequently, if they detect the flaming arrows, they will put them out immediately, which make the flaming arrows useless in most cases. However, with the advent of burning mirror, the situation can be totally different. The Roman navy will only recognize the burning mirror as a mirror, which they probably judge as harmless. And it is through this false prediction that burning mirror can be pretty effective. When their ships are caught on fire, they would be surprised by everything that happened.
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Grammar and spelling errors:
Line 1, column 162, Rule ID: SENTENCE_WHITESPACE
Message: Add a space between sentences
Suggestion: Primarily
... contradicts the readings point of view.Primarily, the lecturer suggests that the mirror ...
^^^^^^^^^
Transition Words or Phrases used:
but, consequently, hence, however, if, second, secondly, so, then, therefore, thus, whereas, in most cases
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 12.0 10.4613686534 115% => OK
Auxiliary verbs: 10.0 5.04856512141 198% => OK
Conjunction : 3.0 7.30242825607 41% => More conjunction wanted.
Relative clauses : 11.0 12.0772626932 91% => OK
Pronoun: 13.0 22.412803532 58% => OK
Preposition: 26.0 30.3222958057 86% => OK
Nominalization: 2.0 5.01324503311 40% => More nominalizations (nouns with a suffix like: tion ment ence ance) wanted.
Performance on vocabulary words:
No of characters: 1231.0 1373.03311258 90% => OK
No of words: 244.0 270.72406181 90% => More content wanted.
Chars per words: 5.04508196721 5.08290768461 99% => OK
Fourth root words length: 3.95227774224 4.04702891845 98% => OK
Word Length SD: 2.57111628309 2.5805825403 100% => OK
Unique words: 137.0 145.348785872 94% => More unique words wanted.
Unique words percentage: 0.561475409836 0.540411800872 104% => OK
syllable_count: 373.5 419.366225166 89% => OK
avg_syllables_per_word: 1.5 1.55342163355 97% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 2.0 3.25607064018 61% => OK
Article: 10.0 8.23620309051 121% => OK
Subordination: 4.0 1.25165562914 320% => Less adverbial clause wanted.
Conjunction: 1.0 1.51434878587 66% => OK
Preposition: 3.0 2.5761589404 116% => OK
Performance on sentences:
How many sentences: 14.0 13.0662251656 107% => OK
Sentence length: 17.0 21.2450331126 80% => The Avg. Sentence Length is relatively short.
Sentence length SD: 53.2175454419 49.2860985944 108% => OK
Chars per sentence: 87.9285714286 110.228320801 80% => OK
Words per sentence: 17.4285714286 21.698381199 80% => OK
Discourse Markers: 7.57142857143 7.06452816374 107% => OK
Paragraphs: 3.0 4.09492273731 73% => More paragraphs wanted.
Language errors: 1.0 4.19205298013 24% => OK
Sentences with positive sentiment : 6.0 4.33554083885 138% => OK
Sentences with negative sentiment : 5.0 4.45695364238 112% => OK
Sentences with neutral sentiment: 3.0 4.27373068433 70% => OK
What are sentences with positive/Negative/neutral sentiment?
Coherence and Cohesion:
Essay topic to essay body coherence: 0.132153847502 0.272083759551 49% => OK
Sentence topic coherence: 0.0490456588323 0.0996497079465 49% => OK
Sentence topic coherence SD: 0.0537989838417 0.0662205650399 81% => OK
Paragraph topic coherence: 0.0911866828673 0.162205337803 56% => OK
Paragraph topic coherence SD: 0.0291350268812 0.0443174109184 66% => OK
Essay readability:
automated_readability_index: 11.1 13.3589403974 83% => Automated_readability_index is low.
flesch_reading_ease: 62.68 53.8541721854 116% => OK
smog_index: 3.1 5.55761589404 56% => Smog_index is low.
flesch_kincaid_grade: 8.7 11.0289183223 79% => OK
coleman_liau_index: 11.71 12.2367328918 96% => OK
dale_chall_readability_score: 8.36 8.42419426049 99% => OK
difficult_words: 60.0 63.6247240618 94% => OK
linsear_write_formula: 11.0 10.7273730684 103% => OK
gunning_fog: 8.8 10.498013245 84% => OK
text_standard: 9.0 11.2008830022 80% => OK
What are above readability scores?
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Minimum four paragraphs wanted. The correct pattern:
para 1: introduction
para 2: doubt 1
para 3: doubt 2
para 4: doubt 3
Less contents wanted from the reading passages(25%), more content wanted from the lecture (75%).
Don't need a conclusion paragraph.
Read sample essays from ETS:
http://www.testbig.com/users/toeflwritingmaster
Rates: 78.3333333333 out of 100
Scores by essay e-grader: 23.5 Out of 30
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Note: the e-grader does NOT examine the meaning of words and ideas. VIP users will receive further evaluations by advanced module of e-grader and human graders.