February 22, 1889.] 



SCIENCE. 



145 



four times, so as to make the scale of the map about three times, 

 that of Angstrom's map. The positives thus made are then fig- 

 ured, and negatives made from them by contact. 



In the negatives so far examined, the scale has been placed with- 

 in less than ^V Angstrom division, or r^V?ni wave-length of its true 

 position. 



As to the definition, much is lost in the enlargement, not so much 

 from want of definition in the enlarging lens, a 25 by 21 inch Dall- 

 meyer, rapid rectilinear, as from the radical defect of photographic 

 processes ; for, when one brings out the fine doubles in which the 

 streak of light in the centre is very faint, he loses many of the fainter 

 lines. The original negatives show E, and even finer lines like 

 that at wave-lengths 5276.1 and 5914-3. plainly double, but there is 

 little hope of showing this on the map. 



The atmospheric line just outside of one of the D lines also nearly 

 merges into it, although in the original negative it is widely sun- 

 dered from it. 



However, there are few instruments which will show more of the 

 spectrum than can be found on the map, even below the D line, 

 where cyanine and chlorophyl plates had to be used, for the first 

 line in B is shown widely triple. Above, and including the D line, 

 the definition rapidly improves, and a low-power magnifier must be 

 used to bring out the full definition. However, from wave-lengths 

 5300 to 3800 the superiority over the old edition is not so marked as 

 above and below this. In the ultra violet above H there is an im- 

 mense improvement in the new, both in definition and in the quality 

 of the photograph. 



As to comparison with other maps of the spectrum made by 

 measurement and drawing, it may be said that no comparison is 

 possible. The photograph is the work of the sunlight itself, and 

 the user of this map has the solar spectrum itself before him, and 

 not a distorted drawing full of errors of wave-length and of inten- 

 sity. The superiority is so great that there is no possibility for 

 comparison. 



The following is a list of the plates, each 3 by 2 feet, containing 

 two strips of the spectrum : a includes from wave-length (?) to 

 3350 ; b, from wave-length 3270 to 3730 ; c, from wave-length 3670 

 to 4130; d, from wave-length 4050 104550; e, from wave-length 

 4450 to 4950 ; y, from wave-length 4850 to 5350; g, from wave- 

 length 5250 to 5750; k, from wave-length 5650 to 6150; z', from 

 wave-length 6050 to 6550; j, from wave-length 6450 to 6950. 



Negatives b, c, d, e,f,g, h, i,j, are now ready, although that for 

 / is too irregular to be entirely satisfactory, and it may be replaced. 

 The plate a to the extremity of the solar spectrum will be attempted 

 this summer, but may cause much trouble and delay, and will be 

 sold as an extra plate. The prints are on heavy albumen paper 

 mounted on cloth. 



The cost of printing has been so much increased that the prices 

 for this new series will be greater than for the old one, but scarcely 

 more than covers the cost of the printing. 



The plates will be delivered in Baltimore or New York, or will 

 be sent by express or mail, securely packed, at the charge and risk 

 of the purchaser, at the following net prices : set of nine plates, 

 wave-length 3270 to 6950, $18; single plates, $2.50. Should any 

 extra plates continuing the spectrum in either direction be published, 

 subscribers can have them at $2 each. Subscribers to the old edi- 

 tion will have the preference in the delivery of the new one, and a 

 reduction of 10 per cent in the price. The three plates h, i,j, to 

 complete their set, will be furnished for $6. They are advised to 

 take g also, as the old map of that region was bad. The ioxix, g, 

 h, i,j, will be furnished to them for $8. 



Two plates, each 3 by 2 feet, suitable for framing and hanging 

 on the wall, have been made of the B and D lines. The latter are 

 3 inches apart, and the former has an extent of about 24 inches. 

 Enlargements of some of the carbon bands from the arc electric 

 light have also been made. They show the wonderful structure of 

 these bands, each containing many hundred lines, each one of which 

 is a close double, or, in some cases, a triple. These plates will be 

 sold for $2.25 unmounted, or $2.50 mounted on cloth. No plate 

 will be given away or sent in exchange. Remittances may be made 

 by draft or money-order. All subscriptions and orders should be 

 sent, and remittances made, to the Publication Agency of the Johns 

 Hopkins University, Baltimore, Md. 



THE EARTHQUAKE OF LIGURIA, FEB. 23, 1887. 



Messrs. T. Taramelli and G. Mercalli have made an ex- 

 haustive report on the earthquake of Liguria in February, 1887, to 

 the Italian Department of the Interior. A geological and an his- 

 torical chapter form the introduction, which is followed by an 

 account of the results of the authors' studies and inquiries. They 

 visited all localities that were severely damaged by the shocks, 

 while information on others, which they were not able to visit, was 

 collected by means of circulars of inquiry. Thus exhaustive re- 

 ports on the character of the earthquake were obtained from over 

 eleven hundred localities. This abundant material, arranged and 

 discussed systematically, forms the basis and the main part of the 

 report. The results of this discussion are summarized by the 

 Naturwissenschaftliche Rundschau as follows : — 



Many insignificant, preparatory shocks preceded the Ligurian 

 earthquakes of 1752 and 1854, as well as that of Feb. 23, 1887. In 

 the night from Feb. 22 to Feb. 23, four light shocks were felt over 

 exactly the same territory that was visited by the severe shocks of 

 the following day. Evidently the seismic centre was in full activity 

 that night ; but there are only four indications, as no seismic instru- 

 ments and observers exist on the Riviera di Ponente. A little while 

 before the earthquake began, the sea was observed to be exception- 

 ally quiet. A few observers claim to have seen unusual lights in 

 the atmosphere. In the regions which suffered most severely, ani- 

 mals were observed to be restless. In a very few places a change 

 of springs was observed. Thermometer and barometer were not 

 influenced by the shocks. 



The principal shock was observed in a circular area cover- 

 ing about 568,000 square kilometres. Its southern limit is Rome 

 and Mount Ferru in Sardinia. Eastward it extends to Pordenone, 

 westward to Perpignan, and northward to Dijon and Basle. The 

 shocks spread with greater force northward to France and western 

 Switzeriand, than southward on the Italian peninsula. According 

 to the intensity of the phenomena, the authors distinguish four 

 zones ; the central region, in which the most formidable destruction 

 took place, forming a zone a hundred kilometres in width along the 

 coast from Mentone to Albissola. It embraces a narrow coast strip,, 

 because the seismic centre was situated in the sea, and because 

 the old crystalline rocks of the Ligurian Apennines reflected the 

 seismic waves. The next zone is called by the investigators the 

 " almost destructive " one. It extends to the hills of Piedmont. 

 Very strong shocks were felt in the third zone, which extends from 

 the second principally north-westward, including Turin and the low- 

 lying Canavese, where the shocks seem to have been increased in 

 violence by waves reflected from the gneissic mass of the Grand 

 Paradiso. The last zone embraces those places in which the earth- 

 quake was felt, but did not do any damage. 



In the whole territory where the earthquake was strongly felt, 

 the first shock lasted thirty seconds, and consisted of two shocks 

 almost immediately following one another. Each of these shocks- 

 caused first a subsultory, then an undulating motion. In no place,- 

 not even in those where the shocks were most destructive. Was the 

 movement vertical. Therefore the resultant of both shocks was- 

 much influenced by local causes, and neighboring places show great 

 differences in the direction of the shocks. The second shock was the 

 stronger one, causing particularly a strong subsultory movement.. 

 Only in Nice and other places in France the first shock was the- 

 strongest. The second part of the shock was everywhere compli- 

 cated by the resultant action of its combination with the first shock. 

 This accounts for the fact that the second shock frequently left the 

 impression of a rotatory movement. In many places, for instance 

 in Mentone, objects lying on the ground have been turned round. 

 In places lying at greater distances from the central point, the 

 vertical component decreased rapidly, but all the other peculiarities 

 of the shock remained. In the outlying zone the slowness and 

 regularity of motion of the shock were remarkable, which caused, 

 pendulums three feet and more in length to swing. 



At various places the horizontal velocity caused by the shock was 

 determined by observations, and by objects thrown some distance. 

 At Oneglia the force was large enough to give a portion of a sill, 

 weighing about five thousand pounds, an initial velocity of thirty- 

 one feet. This horizontal force decreased with increasing dist?nce 



