way Company recovered the portion which was formerly covered and painted the remainder of the pipe which had been exposed.

The insulating coating of asphalt and burlap was removed from pipe No. 780, under the car tracks opposite the car house on Boylston Street, and the pipe was carefully inspected. This pipe was discovered so badly pitted in December, 1902, when the insulating covering was first applied, that the 80 pits in it were carefully dug out and accurately located, and a plan of the outer surface was made for future reference. In April, 1904, the covering was removed from this pipe, and it was carefully examined, and the pits had then increased slightly in depth and considerably in area and number, as a total of 480 were located at that time. After the examination was completed, the Boston Elevated Railway Company recovered the pipe with asphalt and burlap. When examined during the past year the pipe was slightly damp in spots under the covering, and a total of 529 pits were found and accurately located. Of these, about 90 appeared to be new, and some of the old pits had enlarged in area, and in some cases 2 or more of the original pits had united to form a larger one. The depth of the old pits appeared to be only very slightly deeper than in 1904. Seven casts were taken as records of some of the larger and deeper pits, and are comparable with casts which were taken in 1904.

The examinations indicate that the portion of this 48-inch pipe line between Eliot Street in Cambridge and the south shore of the Charles River is in a dangerous condition.

An examination was made of about 150 square feet of pipe surface on the easterly 48-inch low-service pipe line in Middlesex Avenue at Eighth Street in Medford, just north of and on the positive side of an insulating joint located at this place. Thirty-four small pits and 2 distinct rings around the pipe were found, varying from 1% to 16 of an inch in depth, indicating that disintegration of the pipe is going on slowly on the positive section of the pipe line. Three casts were taken as permanent records.

An examination of the 42-inch low-service pipe line in Broadway at Second Street, Chelsea, showed that the pits found at this place in August, 1903, had enlarged in area and increased slightly in depth. Twenty pits were found, varying from 1% to 3% of an inch in depth, in an area of 50 square feet of pipe surface. Four casts were taken of the larger pits for comparison with casts made in

August, 1903. At the corner of Broadway and Williams Street about 150 square feet of pipe surface was examined on the 42-inch low-service main. The action at this point is quite uniform over the entire surface of the pipes. It was possible to cut into the pipe almost anywhere to a depth of % of an inch or more.

The 24-inch pipe in Broadway, south of Williams Street, is known to be in bad condition, but was not examined because it would have been necessary to disturb a new and expensive pavement which had been recently laid.

An examination was made of the 24-inch pipes crossing Chelsea Creek on December 18, and several casts were taken showing the condition of the pipes. The older pipe line is in a treacherous condition near low-water line, the material being very soft, so that it can readily be cut out to a depth of half an inch.

Measurements made during the year of the amount of electricity flowing on the pipes indicate that the disintegration of the 16-inch and 12-inch high-service pipe lines in Broad and Washington streets in Lynn is progressing at about the same rate as last year, but the pipes have not been examined because to do so it would have been necessary to disturb new and expensive pavements.

GYPSY AND BROWN-TAIL MOTHS.

The protection of the trees on the property of the Metropolitan Water Works from the ravages of the gypsy and brown-tail moths has required an expenditure of approximately $10,700, which has been distributed as follows:

Reservoirs in Framingham, Ashland and Hopkinton, .
Wachusett Reservoir and Aqueduct,

50

500

$10,700

The cost of work done at Spot Pond was about $4,000 less than during the previous year, and it was also less at Mystic Lake, reservoir and pumping station, but on other parts of the works there was

an increase in cost, due to the spread of moths and to an advance of from 10 to 1212 per cent. in the rate of wages.

In the vicinity of Boston natural causes have reduced the browntail moths to a very small percentage of the number which infested the trees two years ago, while in Framingham, Southborough and Clinton they have increased in numbers. The thorough work of destroying the gypsy moths which has been carried on during previous years on the property of the Board at Spot Pond, and on lands in Medford, Arlington and Somerville, has resulted in reducing the number of these moths to comparatively small numbers, and the reduction in cost in 1907 will be followed by a still further reduction during the coming year. There has, on the other hand, been a large increase in the number of gypsy moths in Newton, Weston, Natick and Framingham, through which the aqueducts pass. The cost of protecting the 220 acres at the Weston Reservoir, and along the Weston Aqueduct between the reservoir and the terminal chamber, was about $1,300, or more than double the amount expended in 1906. No gypsy moths have been found on Water Works property west of Framingham, but 9,500 nests of the brown-tail moths were destroyed at the Sudbury Reservoir, and the nests have been destroyed in considerable and increasing numbers at the Hopkinton Reservoir, along the line of the Wachusett Aqueduct in Southborough and Northborough, and in Clinton in the vicinity of the Wachusett Reservoir.

The methods employed for destroying and preventing the spreading of the moths have been as follows:

At Spot Pond the egg clusters of the gypsy moths were painted during the winter with a mixture of creosote and fuel oil. During the latter part of April and the early part of May, 1,900 pounds of tanglefoot were used in banding the trees, at a cost, including labor, of about $675. Lines of boards set on edge and smeared with tanglefoot, which had proved very effective in 1906, were placed along the lines of adjoining property where the moths were very prevalent. During June and July the trees on 23 acres were sprayed with arsenate of lead. The trees on the ground at Mystic Lake, Mystic pumping station and reservoir, and at the Chestnut Hill and Weston reservoirs, were treated in a similar manner. Along the line of the aqueducts and at Lake Cochituate the egg clusters of the gypsy moths were painted with creosote, and at Lake Cochituate 5,700 trees were

banded with burlap. More than 20,000 caterpillars were destroyed along the lines of the aqueducts, at Lake Cochituate and the reservoirs in Framingham, Southborough and Clinton.

Considerable work has been done, particularly along the lines of the aqueducts, in cutting underbrush and undesirable trees, as experience has shown that the suppression of the gypsy moth is very difficult wherever there is a thick growth of underbrush, and the unnecessary trees afford lodging places for the moths and increase the cost of maintaining the works.

CLINTON SEwerage.

The Clinton sewage disposal works were in daily operation throughout the year. The quantity of sewage pumped on the filter-beds was 867,000 gallons per day, an increase of 72,000 gallons per day over the preceding year, and of 123,000 gallons per day over the average since the plant was put into operation in 1899. This increase was due to leakage of ground water into the sewers during the months of October, November and December, when the rainfall was abnormally large. The daily average quantity pumped during these months was 1,161,000 gallons, as compared with a daily average of 528,000 gallons during the month of August.

Following are statistics relating to the operation of the pumping station:

Daily average quantity of sewage pumped (gallons),

Daily average quantity of coal consumed (pounds),

Gallons pumped per pound of coal,

Number of days pumping,

Cost of pumping:

Labor,

Fuel,

Repairs and small supplies, .

Total for station,

Cost per million gallons pumped,

Cost per million gallons raised 1 foot high,

867,000

1,457

595

365

$1,856 76

1,470 05

1,252 95

$4,579 76

$14 47

0 28

The cost of pumping was considerably in excess of that during any previous year, due to increased rate of wages, additional labor and fuel, due to shorter hours of labor and the larger quantity of sewage pumped, and to the cost of new pump plungers, diaphragms

and valves. Repairs were made to the chimney of the pumping station in May, consisting of pointing, painting and oiling the brickwork, cleaning and painting the cast-iron cap and cleaning the interior.

Filter-beds.

The sewage was applied on the filter-beds in practically the same manner as during the preceding year until July 2, when, upon the recommendation of the Chief Engineer of the State Board of Health, radical changes were made in the method of applying the sewage, continuing to the end of the year.

The eight settling basins into which the sewage is pumped were used in rotation continuously throughout the year. During January, February and March the sewage was turned through one of the basins for two weeks, when it was drained off and another basin was used. During the remainder of the year, until December, two basins were used at a time for a period of one week, when they were drained and two others put into use; this method being adopted so as to decrease the velocity of the sewage while passing through the basins and thus increase the amount of sludge collected. During December two basins were used jointly for four weeks, then drained and two others put into use. By this method the eight basins can be used to care for the sludge during the winter, when it is impossible to clean them. The sludge accumulated in the settling basins has been given to the neighboring farmers, who are becoming from year to year more anxious to obtain this material for use on their farms.

Previous to April 19, at times when the temperature was below 15 degrees above zero, practically all of the sewage of each day's pumping was applied to one of five beds, which had been prepared with furrows 3 feet 6 inches apart, the average amount per application being 507,000 gallons, and each bed was used about once in nine days. When the temperature was higher than 15 degrees above zero the sewage was applied to the other or flat beds for about two and one-half hours, the amount per application being 313,000 gallons, and each bed was used about once in twelve and one-half days, which gives an average of about 25,000 gallons per acre per day. The amount of sewage applied to a bed at one time during this method of application varied with the severity of the winter from one and onehalf hours to two and one-half hours. As the winter was very cold it was necessary when applying sewage to the flat beds to make the quantities large, in order to keep the beds open.