punctuation: comma

punctuation: comma

Some ways of using commas:
  • We use commas (,) to separate things in a series or list. We do not use them between the last two words or expressions (except when these are long).
      I went to Spain, Italy, Switzerland, Austria and Germany.
      You had a holiday at Christmas, at New Year and at Easter.
      I spent yesterday playing cricket, listening to jazz records, and talking about the meaning of life.
    We separate adjectives by commas after a noun, but not always before. Compare:
      a tall(,) dark(,) handsome cowboy
      The cowboy was tall, dark and handsome.
      We put commas in a series of colour adjectives.
      a green, red and gold carpet
  • If we put adverbs in unusual places in a clause, we often put commas before and after them.
      My father, however, did not agree.
      Jane had, surprisingly, paid for everything.
      We were, believe it or not, in love with each other.
  • In sentences that begin with conjunctions, we usually put a comma after the first clause.
      If you're ever in London, come and see me.
      As soon as we stop, get out of the car.
  • We do not put commas before 'reported speech' clauses.
      Everybody realized that I was a foreigner.
      (NOT Everybody realized, that . . .)
      I didn't know where I should go.
  • We do not usually use commas between grammatically separate sentences (in places where a full stop would be possible).
      The blue dress was warmer. On the other hand, the purple one was prettier.
      (OR The blue dress was warmer; on the other hand . . . )
  • In numbers, we often use a comma after the thousands.
      3,164 = three thousand, one hundred and sixty-four
      We do not use commas in decimals.
      3-5 = three point five or three and a half.
  • --- >>>
  • 'copula1 verbs
  • 'social' language
  • (a) few and (a) little
  • (a)round and about
  • (be) used to + noun or... -ing
  • (Great) Britain, the United Kingdom, the British Isles and England
  • -ing form ('gerund')
  • -ing form after to
  • -ing form or infinitive?
  • abbreviations
  • about to
  • above and over
  • across and over
  • across and through
  • active verb forms
  • actual(ly)
  • adjectives ending in -Iy
  • adjectives without nouns
  • adjectives: order
  • adjectives: position
  • adverbs of manner
  • adverbs: position (details)
  • adverbs: position (general)
  • after (conjunction)
  • after (preposition); afterwards (adverb)
  • after all
  • afternoon, evening and night
  • ages
  • ago
  • all (of) with nouns and pronouns
  • all and every
  • all and whole
  • all right
  • all with verbs
  • all, everybody and everything
  • almost and nearly
  • also, as well and too
  • although and though
  • among and between
  • and
  • and after try, wait, go etc
  • another
  • any (= 'it doesn't matter which')
  • any and no: adverbs
  • appear
  • articles: a and an; pronunciation of the
  • articles: a/an
  • articles: countable and uncountable nouns
  • articles: introduction
  • articles: special rules and exceptions
  • articles: talking in general
  • articles: the
  • articles: the difference between a/an and the
  • as and like
  • as if and as though
  • as much/many ... as ...
  • as well as
  • as, because and since (reason)
  • as, when and while (things happening at the same time)
  • as...as ...
  • ask
  • at all
  • at, in and on (place)
  • at, in and on (time)
  • be + infinitive
  • be with auxiliary do
  • be: progressive tenses
  • because and because of
  • before (adverb)
  • before (conjunction)
  • before (preposition) and in front of
  • begin and start
  • big, large, great and tall
  • born
  • borrow and lend
  • both (of) with nouns and pronouns
  • both with verbs
  • both... and...
  • bring and take
  • British and American English
  • broad and wide
  • but = except
  • by: time
  • can and could: ability
  • can and could: forms
  • can with remember, understand, speak, play, see, hear, feel, taste and smell
  • can: permission, offers, requests and orders
  • can: possibility and probability
  • close and shut
  • come and go
  • comparison: comparative and superlative adjectives
  • comparison: comparative and superlative adverbs
  • comparison: much, far etc with comparatives
  • comparison: using comparatives and superlatives
  • conditional
  • conjunctions
  • contractions
  • countable and uncountable nouns
  • country
  • dare
  • dates
  • determiners
  • discourse markers
  • do + -ing
  • do and make
  • do: auxiliary verb
  • during and for
  • during and in
  • each and every
  • each other and one another
  • each: grammar
  • either... or...
  • either: determiner
  • ellipsis (leaving words out)
  • else
  • emphasis
  • emphatic structures with it and what
  • enjoy
  • enough
  • even
  • eventual(ly)
  • ever
  • every and every one
  • except
  • except and except for
  • exclamations
  • excuse me, pardon and sorry
  • expect, hope, look forward, wait, want and wish
  • explain
  • fairly, quite, rather and pretty
  • far and a long way
  • farther and further
  • fast
  • feel
  • fewer and less
  • for + object + infinitive
  • for, since, from, ago and before
  • for: purpose
  • future perfect
  • future progressive
  • future: introduction
  • future: present progressive and going to
  • future: shall and will (interpersonal uses)
  • future: shall/will (predictions)
  • future: simple present
  • gender (masculine and feminine language)
  • get (+ object) + verb form
  • get + noun, adjective, adverb particle or preposition
  • get and go: movement
  • go ... -ing
  • go meaning'become'
  • go: been and gone
  • had better
  • half (of)
  • hard and hardly
  • have (got) to
  • have (got): possession, relationships etc
  • have + object + verb form
  • have: actions
  • have: auxiliary verb
  • have: introduction
  • hear and listen (to)
  • help
  • here and there
  • holiday and holidays
  • home
  • hope
  • how and what... like?
  • if only
  • if so and if not
  • if-sentences with could and might
  • if: ordinary tenses
  • if: special tenses
  • ill and sick
  • imperative
  • in and into (prepositions)
  • in case
  • in spite of
  • indeed
  • infinitive after who, what, how etc
  • infinitive of purpose
  • infinitive without to
  • infinitive: negative, progressive, perfect, passive
  • infinitive: use
  • instead of... -ing
  • inversion: auxiliary verb before subject
  • inversion: whole verb before subject
  • irregular verbs
  • it's time
  • it: preparatory object
  • it: preparatory subject
  • last and the last
  • let's
  • letters
  • likely
  • long and for a long time
  • look
  • look (at), watch and see
  • marry and divorce
  • may and might: forms
  • may and might: permission
  • may and might: probability
  • mind
  • modal auxiliary verbs
  • more (of): determiner
  • most (of): determiner
  • much (of), many (of): determiners
  • much, many, a lot etc
  • must and have to; mustn't, haven't got to, don't have to, don't need to and needn't
  • must: deduction
  • must: forms
  • must: obligation
  • names and titles
  • nationality words
  • need
  • negative questions
  • negative structures
  • neither (of): determiner
  • neither, nor and not... either
  • neither... nor...
  • next and nearest
  • next and the next
  • no and none
  • no and not
  • no and not a/not any
  • no more, not any more, no longer, not any longer
  • non-progressive verbs
  • noun + noun
  • numbers
  • once
  • one and you: indefinite personal pronouns
  • one: substitute word
  • other and others
  • ought
  • own
  • participle clauses
  • participles used as adjectives
  • participles: 'present' and 'past' participles (-ing and -ed)
  • passive structures: introduction
  • passive verb forms
  • past tense with present or future meaning
  • past time: past perfect simple and progressive
  • past time: past progressive
  • past time: present perfect progressive
  • past time: present perfect simple
  • past time: simple past
  • past time: the past and perfect tenses (introduction)
  • perfect tenses with this is the first time..., etc
  • personal pronouns (I, me, it etc)
  • play and game
  • please and thank you
  • possessive with determiners (a friend of mine, etc)
  • possessive's: forms
  • possessive's: use
  • possessives: my and mine, etc
  • prepositional verbs and phrasal verbs
  • prepositions after particular words and expressions
  • prepositions and adverb particles
  • prepositions at the end of clauses
  • prepositions before particular words and expressions
  • prepositions: expressions without prepositions
  • present tenses: introduction
  • present tenses: present progressive
  • present tenses: simple present
  • progressive tenses with always
  • punctuation: apostrophe
  • punctuation: colon
  • punctuation: comma
  • punctuation: dash
  • punctuation: quotation marks
  • punctuation: semi-colons and full stops
  • question tags
  • questions: basic rules
  • questions: reply questions
  • questions: word order in spoken questions
  • quite
  • real(ly)
  • reflexive pronouns
  • relative pronouns
  • relative pronouns: what
  • relative pronouns: whose
  • relatives: identifying and non-identifying clauses
  • remind
  • reported speech and direct speech
  • reported speech: orders, requests, advice etc
  • reported speech: pronouns; 'here and now' words; tenses
  • reported speech: questions
  • requests
  • road and street
  • say and tell
  • see
  • seem
  • shall
  • short answers
  • should
  • should after why and how
  • should and would
  • should, ought and must
  • should: (If I were you) I should ...
  • similar words
  • since (conjunction of time): tenses
  • singular and plural: anybody etc
  • singular and plural: irregular plurals
  • singular and plural: plural expressions with singular verbs
  • singular and plural: pronunciation of plural nouns
  • singular and plural: singular words ending in -s
  • singular and plural: singular words with plural verbs
  • singular and plural: spelling of plural nouns
  • slow(ly)
  • small and little
  • smell
  • so am I, so do I etc
  • so and not with hope, believe etc
  • some and any
  • some/any and no article
  • some: special uses
  • somebody and anybody, something and anything, etc
  • sound
  • spelling and pronunciation
  • spelling: -ise and -ize
  • spelling: -ly
  • spelling: capital letters
  • spelling: ch and tch, k and ck
  • spelling: doubling final consonants
  • spelling: final -e
  • spelling: full stops with abbreviations
  • spelling: hyphens
  • spelling: ie and ei
  • spelling: y and i
  • still, yet and already
  • subject and object forms
  • subjunctive
  • such and so
  • suggest
  • surely
  • sympathetic
  • take
  • take (time)
  • tall and high
  • taste
  • telephoning
  • telling the time
  • tenses in subordinate clauses
  • that: omission
  • the same
  • there is
  • think
  • this and that
  • too
  • travel, journey and trip
  • unless and if not
  • until and by
  • until and to
  • used to + infinitive
  • verbs with object complements
  • verbs with two objects
  • way
  • weak and strong forms
  • well
  • when and if
  • whether and if
  • whether... or...
  • which, what and who: question words
  • who ever, what ever, how ever etc
  • whoever, whatever, whichever, however, whenever and wherever
  • will
  • wish
  • worth ... -ing
  • would
  • would rather
  • My Account / Test History


    Simple Science

    The Bursting of Dams and Reservoirs

    The Water Problem of a Large City:
    The construction of a safe reservoir is one of the most important problems of engineers. In October, 1911, a town in Pennsylvania was virtually wiped out of existence because of the bursting of a dam whose structure was of insufficient strength to resist the strain of the vast quantity of water held by it. A similar breakage was the cause of the fatal Johnstown flood in 1889, which destroyed no less than seven towns, and in which approximately 2000 persons are said to have lost their lives.

    Water presses not only on the bottom of a vessel, but upon the sides as well; a bucket leaks whether the hole is in its side or its bottom, showing that water presses not only downward but outward. Usually a leak in a dam or reservoir occurs near the bottom. Weak spots at the top are rare and easily repaired, but a leak near the bottom is usually fatal, and in the case of a large reservoir the outflowing water carries death and destruction to everything in its path.

    If the leak is near the surface, as at a, the water issues as a feeble stream, because the pressure against the sides at that level is due solely to the relatively small height of water above a. If the leak is lower, as at b, the issuing stream is stronger and swifter, because at that level the outward pressure is much greater than at a, the increase being due to the fact that the height of the water above b is greater than that above a. If the leak is quite low, as at c, the issuing stream has a still greater speed and strength, and gushes forth with a force determined by the height of the water above c.

    The dam at Johnstown was nearly 1/2 mile wide, and 40 feet high, and so great was the force and speed of the escaping stream that within an hour after the break had occurred, the water had traveled a distance of 18 miles, and had destroyed property to the value of millions of dollars.

    If a reservoir has a depth of 100 feet, the pressure exerted upon each square foot of its floor is 62.5 100, or 6250 pounds; the weight therefore to be sustained by every square foot of the reservoir floor is somewhat more than 3 tons, and hence strong foundations are essential. The outward lateral pressure at a depth of 25 feet would be only one fourth as great as that on the bottom - hence the strain on the sides at that depth would be relatively slight, and a less powerful construction would suffice. But at a depth of 50 feet the pressure on the sides would be one half that of the floor pressure, or 1-1/2 tons. At a depth of 75 feet, the pressure on the sides would be three quarters that on the bottom, or 2-1/4 tons. As the bottom of the reservoir is approached, the pressure against the sides increases, and more powerful construction becomes necessary.

    Small elevated tanks, like those of the windmill, frequently have heavy iron bands around their lower portion as a protection against the extra strain.

    Before erecting a dam or reservoir, the maximum pressure to be exerted upon every square inch of surface should be accurately calculated, and the structure should then be built in such a way that the varying pressure of the water can be sustained. It is not sufficient that the bottom be strong; the sides likewise must support their strain, and hence must be increased in strength with depth. This strengthening of the walls is seen clearly in the reservoir shown in Figure 152. The bursting of dams and reservoirs has occasioned the loss of so many lives, and the destruction of so much property, that some states are considering the advisability of federal inspection of all such structures.

    FIG. - The flow from an opening depends upon the height of water above the opening.

    LIST OF SYNONYMS (A & B )



































































































    WordSynonymWordSynonym
    AbroadOverseasAwayAbsent
    AdmitConfessAwfulTerrible
    AgreeConsentBabyInfant
    AlikeSameBackboneSpine
    AllowPermitBeautifulPretty
    AlmostNearlyBeginStart
    AmountQuantityBehaveAct
    AngryMadBellyStomach
    AnnoyIrritateBigLarge
    AnswerReplyBlankEmpty
    AppearSeemBraveBold
    ArriveReachBroadWide
    AskInquireBucketPail
    AssureGuaranteeBusinessTrade
    AttireDressBusyActive

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