The murderer’s object was to get rid of the crate. Would he, therefore, choose a rising or half tide which might drift it back inshore? Surely not; he would select one which would take it as far as possible out to sea. French felt that only ebb tides need be considered. He turned again to Manners.
“I suppose a good ebb develops some strong currents in these channels?”
“You may say so, Mr. French. An average of five knots you may reckon on. A deal faster than you could walk.”
“Five knots an hour?”
“No, sir. Five knots. It’s like this ’ere. A knot ain’t a distance; it’s a speed. If I say five knots I mean five sea miles an hour.”
“A sea mile is longer than an ordinary one?”
“That’s right. It varies in different places, but you may take it as six thousand and eighty feet ’ere.”
French made a short calculation.
“That is about five and three-quarters English miles per hour,” he remarked as he scaled this distance up the Inlet from the position of the crate. And then his interest quickened suddenly.
A little over five miles from the point at which the crate had sunk the estuary narrowed to less than a quarter of a mile in width. At this point it was crossed by two bridges, carrying, respectively, the main road and the railway between Swansea and Llanelly. Had the crate been thrown from one of these?
French saw at once that no more suitable place for the purpose could be found. Objects pushed in from the bank would tend to hug the shore and to be caught in backwaters or eddies. Moreover, even if they escaped such traps they would not travel at anything like the maximum speed of the current. But from a bridge they could be dropped into the middle of the stream where the flow was quickest.
“What about the bridge up at Loughor?” he asked. “If the crate was dropped off that on an ebb tide, do you think it would get down all right?”
Manners was impressed by the suggestion. Given a good ebb, about an hour should carry the crate to where it was found. French rose with sudden energy.
“Let’s go and see the place. How soon can we get there?”
By a stroke of luck a train was approaching as they entered the station, and twenty minutes later they reached their destination.
Loughor proved to be a straggling village situated on the left bank of the estuary where the latter made a right-angled bend towards the north. The two bridges ran side by side and a couple of hundred yards apart. That carrying the road was a fine wide structure of ferroconcrete, fairly new and leading directly into the village. The railway bridge was lower downstream, considerably older, and supported on timber piles. Both were about three hundred yards long, and built with short spans and many piers. The tide was out and the usual wide mudbanks were exposed on either shore.
Directly French saw the spot he felt that here indeed was what he sought. On a dark night it would have been easy to drop the crate from the road bridge in absolute secrecy. Nor, as far as he could see from the map, was there any other place from which it could have been done.
He had assumed that the criminal would select an ebb tide for his attempt, in order to ensure the crate being carried as far as possible out to sea. For the same reason French believed he would choose the time of its most rapid run. That time must also be in the dead of night to minimise the risk of discovery from passing road traffic. From to would probably best meet the conditions, as the chances were a thousand to one that the road would then be deserted.
French wondered if he could get anything from these considerations. He turned to Manners.
“I suppose it takes a bit of time to get up a good run in an estuary like this? How soon after high water would you say the current was running at full speed under the bridge?”
“From one to two hours, more or less.”
One to two hours previous to the period to meant between and
“Now, Mr. Manners, can you tell me whether high water fell between and on any night about five or six weeks ago?”
Manners once more produced his tide table.
“Five or six weeks ago,” he repeated, slowly. “That would be between the and the .” He ran his stubby finger up the pages, then read out: “ ‘—that’s five minutes past midnight, you understand. ; ’ ’Ow would that suit you, sir?”
“All right, I think,” French answered as he noted the three dates. “Any of those top springs?”
“No, sir; you don’t get ’igh water of springs at night. ’Bout six or seven o’clock it runs. Those dates wot I gave you are about dead neaps.”
“But there is still a strong flow at neaps?”
“Oh, bless you, yes! Not so strong as at springs, o’ course, but plenty strong enough.”
All this seemed satisfactory to French and he felt a growing conviction that the small hours of the , , or had witnessed the launch of the crate. But this was mere theory, and theory is popularly admitted to be worth only one-sixteenth of the value of practice. Could not he arrive at something more definite?
Suddenly he thought he saw his way.
“You say it was neap tides on those three dates in ? What rise and fall does that represent?”
“ ’Bout eighteen feet.”
“How soon shall we have that again?”
“Not for nearly a week we shan’t. Say next Monday.”
“I can’t wait
